Pediatric Thalassemia 

Updated: Aug 23, 2017
Author: Hassan M Yaish, MD; Chief Editor: Max J Coppes, MD, PhD, MBA 

Overview

Practice Essentials

The thalassemias are inherited disorders of hemoglobin (Hb) synthesis. Their clinical severity widely varies, ranging from asymptomatic forms to severe (see the image below) or even fatal entities.

Peripheral blood film in Cooley anemia. Peripheral blood film in Cooley anemia.

Signs and symptoms

The clinical picture of the thalassemias varies widely, depending on the severity of the condition and the age at diagnosis. In the more severe forms of the disease (eg, β-thalassemia major), symptoms vary from extremely debilitating in patients who are not receiving transfusions to mild and almost asymptomatic in those receiving regular transfusion regimens and closely monitored chelation therapy.

Signs and symptoms of different types of thalassemia include the following:

  • More severe forms: Some pallor, slight scleral icterus, enlarged abdomen

  • Rare types of β-thalassemia trait: Severe hemolytic process requiring management, such as thalassemia intermedia or thalassemia major

  • Hb E/β thalassemia: May have severe symptoms and clinical course identical to that of β-thalassemia major

  • Heterozygous/homozygous Hb E: Usually slightly anemic and usually asymptomatic

  • Α-Thalassemia: Clearly evident hematologic abnormalities in newborns with mild or moderate forms of the disease

  • Β-Thalassemia: Extreme pallor, swollen abdomen due to hepatosplenomegaly

  • Severe bony changes due to ineffective erythroid production (eg, frontal bossing, prominent facial bones, dental malocclusion)

  • Hypermetabolism from ineffective erythropoiesis

  • Gout due to hyperuricemia (occasionally)

  • Iron overload: One of the major causes of morbidity in all patients with severe forms of thalassemia

  • Growth retardation, failure to thrive

  • Metabolic symptoms that suggest diabetes, thyroid disorder, or other endocrinopathy

  • Neuropathy/paralysis in patients with severe anemia not receiving transfusion therapy

See Clinical Presentation for more detail.

Diagnosis

The diagnosis of thalassemia is made through studies such as bone marrow examination, hemoglobin electrophoresis, and iron count. The CBC count and peripheral blood film examination results are usually sufficient to suspect the diagnosis. Hb evaluation confirms the diagnosis in β-thalassemia, Hb H disease, and Hb E/β thalassemia.

Classification of thalassemia

Although there are many types of thalassemic syndromes, each involves decreased production of one globin chain or more, which form the different Hbs normally found in RBCs. In clinical practice, the most important types affect either α- or β-chain synthesis.

The most common forms of α-thalassemia are as follows:

  • Silent carrier α-thalassemia: The diagnosis cannot be confirmed based on Hb electrophoresis results, which are usually normal in all α-thalassemia traits

  • Α-Thalassemia trait: Characterized by mild anemia and low RBC indices

  • Hb H disease: Represents α-thalassemia intermedia, with mildly to moderately severe anemia, splenomegaly, icterus, and abnormal RBC indices

  • Α-Thalassemia major: Results in the severe form of homozygous α-thalassemia

Some of the more common forms of β-thalassemia are as follows:

  • Silent carrier β-thalassemia: Patients are asymptomatic, except for possible low RBC indices

  • Β-Thalassemia trait: Patients have mild anemia, abnormal RBC indices, and abnormal Hb electrophoresis results with elevated levels of Hb A2, Hb F, or both

  • Thalassemia intermedia: Patients have anemia of intermediate severity

  • Β-thalassemia associated with β-chain structural variants: The most significant condition in this group of thalassemic syndromes is the Hb E/β thalassemia

  • Thalassemia major (Cooley anemia): This condition is characterized by transfusion-dependent anemia, massive splenomegaly, bone deformities, growth retardation, and peculiar facies in untreated individuals, 80% of whom die within the first 5 years of life from complications of anemia

Staging

  • Stage I patients: Received fewer than 100 units of packed red blood cells; usually asymptomatic

  • Stage II patients: Received 100-400 units of blood; may report slight fatigue

  • Stage III patients: Have symptoms ranging from palpitations to CHF

The Lucarelli classification is used for patients with severe disease who are candidates for hematopoietic stem cell transplantation.[1]

Laboratory studies

  • CBC count

  • Hb electrophoresis

  • Peripheral blood smear

  • Iron studies (ie, levels of serum iron, serum ferritin)

  • Complete RBC phenotype

  • Hepatitis screen

  • Folic acid level

  • level of urinary excretion of iron after deferoxamine challenge

  • HLA typing before initiation of blood transfusion therapy

  • Renal function tests during chelation therapy

Imaging studies

  • Skeletal survey: Reveals classic bony changes in patients who are not regularly transfused

  • Chest radiography: To evaluate cardiac size and shape

  • MRI or CT scanning of affected areas: To diagnose complications (eg, bony deformities, compression fractures)

  • R2 MRI: For noninvasive measurement of liver and cardiac iron overload and to monitor response to iron chelation therapy (eg, FerriScan)

  • T2* MRI: Could evaluate both liver and cardiac iron load simultaneously[2]

  • ECG, echocardiography: To monitor cardiac function

Procedures

  • Bone marrow examination: To exclude other conditions that may manifest as thalassemia major

  • Liver biopsy: To assess iron deposition and the degree of hemochromatosis

See Workup for more detail.

Management

Patients with thalassemia traits do not require medical or follow-up care after the initial diagnosis is made. Do not initiate iron therapy unless a definite deficiency is confirmed.

Patients with severe thalassemia require medical treatment. Regular blood transfusion combined with well-monitored chelation therapy is the standard therapy.

Pharmacotherapy

  • Antipyretics, analgesics (eg, acetaminophen)

  • Antihistamines (eg, diphenhydramine)

  • Chelating agents (eg, deferoxamine, deferasirox)

  • Corticosteroids (eg, hydrocortisone)

  • Antibacterial combinations (eg, TMP/SMX, gentamicin, penicillin V)

  • Vitamins (eg, ascorbic acid, alpha-tocopherol, folic acid)

  • Vaccines (eg, polyvalent pneumococcal; 7-valent pneumococcal conjugated; H influenzae type B; meningitis group A, C, Y, and W-135)

  • Antineoplastics (eg, hydroxyurea)

  • Growth hormone (eg, somatropin)

The FDA has expanded the approved use of deferasirox to treat children aged 10 years and older with chronic iron overload due to nontransfusion-dependent thalassemia (NTDT). The agency recommends administration of deferasirox in such children who have a hepatic iron concentration of at least 5 mg of iron per gram of dry liver weight. Previously, deferasirox was approved for managing chronic iron overload due to blood transfusions in patients ages 2 years and older.[3, 4]

Surgical options

  • Splenectomy: Principal surgical procedure for many patients with thalassemia

  • Placement of central line: For the ease and convenience of administering blood transfusions, chelation therapy, or both in patients with severe thalassemia on transfusion therapy

See Treatment and Medication for more detail.

Background

The thalassemias are inherited disorders of hemoglobin (Hb) synthesis. Their clinical severity widely varies, ranging from asymptomatic forms to severe or even fatal entities. The name Mediterranean anemia, which Whipple introduced, is misleading because the condition can be found in any part of the world. As described below, different types of thalassemia are more endemic to certain geographic regions.

In 1925, Thomas Cooley, a Detroit pediatrician, described a severe type of anemia in children of Italian origin. He noted abundant nucleated red blood cells (RBCs) in the peripheral blood, which he initially thought was erythroblastic anemia, an entity that von Jaksh described earlier. Before long, Cooley realized that erythroblastemia is neither specific nor essential in this disorder and that the term erythroblastic anemia was nothing but a diagnostic catchall. Although Cooley was aware of the genetic nature of the disorder, he failed to investigate the apparently healthy parents of the affected children.

In Europe, Riette described Italian children with unexplained mild hypochromic and microcytic anemia in the same year Cooley reported the severe form of anemia later named after him. In addition, Wintrobe and coworkers in the United States reported a mild anemia in both parents of a child with Cooley anemia. This anemia was similar to the one that Riette described in Italy. Only then was Cooley's severe anemia recognized as the homozygous form of the mild hypochromic and microcytic anemia that Riette and Wintrobe described. This severe form was then labeled as thalassemia major and the mild form as thalassemia minor. The word thalassemia is a Greek term derived from thalassa, which means "the sea" (referring to the Mediterranean), and emia, which means "related to blood."

These initial patients are now recognized to have been afflicted with β thalassemia. In the following few years, different types of thalassemia that involved polypeptide chains other than β chains were recognized and described in detail.

In recent years, the molecular biology and genetics of the thalassemia syndromes have been described in detail, revealing the wide range of mutations encountered in each type of thalassemia, depicted in the image below.

Various mutations in the beta gene that result in Various mutations in the beta gene that result in beta thalassemia.

β thalassemia alone can arise from any of more than 150 mutations.

Pathophysiology

The thalassemias are inherited disorders of Hb synthesis that result from an alteration in the rate of globin chain production. A decrease in the rate of production of a certain globin chain or chains (α, β, γ, δ) impedes Hb synthesis and creates an imbalance with the other, normally produced globin chains.

Because 2 types of chains (α and non-α) pair with each other at a ratio close to 1:1 to form normal Hbs, an excess of the normally produced type is present and accumulates in the cell as an unstable product, leading to the destruction of the cell. This imbalance is the hallmark of all forms of thalassemia. For this reason, most thalassemias are not considered hemoglobinopathies because the globin chains are normal in structure and because the defect is limited to a decreased rate of production of these normal chains. However, thalassemic hemoglobinopathies are recognized, as discussed below.

The type of thalassemia usually carries the name of the underproduced chain or chains. The reduction varies from a slight decrease to a complete absence of production. For example, when β chains are produced at a lower rate, the thalassemia is termed β+, whereas β-0 thalassemia indicates a complete absence of production of β chains from the involved allele.

The consequences of impaired production of globin chains ultimately result in the deposition of less Hb into each RBC, leading to hypochromasia. The Hb deficiency causes RBCs to be smaller, leading to the classic hypochromic and microcytic picture of thalassemia. This is true in almost all anemias caused by impairment in production of either of the 2 main components of Hb: heme or globin. However, this does not occur in the silent carrier state, since both Hb level and RBC indices remain normal.

In the most common type of β thalassemia trait, the level of Hb A2 (δ2/α2) is usually elevated. This is due to the increased use of δ chains by the excessive free α chains, which results from a lack of adequate β chains with which to pair. The δ gene, unlike β and α genes, is known to have a physiologic limitation in its ability to produce adequate δ chains; by pairing with the α chains, δ chains produce Hb A2 (approximately 2.5-3% of the total Hb).

Some, but not all, of the excessive α chains are used to form Hb A2 with the δ chains, whereas the remaining α chains precipitate in the cells, reacting with cell membranes, intervening with normal cell division, and acting as foreign bodies, leading to destruction of RBCs. The degree of toxicity caused by the excessive chains varies according to the type of such chains (eg, the toxicity of α chains in β thalassemia is more prominent than the toxicity of β chains in α thalassemia).

β thalassemia is mostly related to a point mutation in the β globin gene. However, large deletions that may involve the entire β gene, or even extend to delete the neighboring δ gene, have been previously reported. Four new such mutations were identified in French patients. In 3 of these mutations, the deletion has extended to involve the δ gene, resulting in failure to produce any Hb A2. In such cases, the β/δ thalassemia is to be differentiated from the phenotypically similar condition known as hereditary persistence of fetal hemoglobin (HPFH). The importance of differentiating the conditions is reflected in prenatal and newborn screening for hemoglobinopathy.[5]

In the severe forms, such as β thalassemia major or Cooley anemia, the same pathophysiology applies with substantial exaggeration. The significant excess of free α chains caused by the deficiency of β chains causes destruction of the RBC precursors in the bone marrow (ie, ineffective erythropoiesis).

Globin chain production

To understand the genetic changes that result in thalassemia, one should be familiar with the physiologic process of globin chain production in the healthy individual. The globin chain as a unit is a major building block for Hb: together with heme, it produces the Hb molecule (heme plus globin equals Hb). Two different pairs of globin chains form a tetrameric structure with a heme moiety in the center. All normal Hbs are formed from 2 α-like chains and 2 non-α chains. Various types of Hb are formed, depending on the types of chains pairing together. Such Hbs exhibit different oxygen-binding characteristics, normally related to the oxygen delivery requirement at different developmental stages in human life.

In embryonic life, ζ chains (α-like chains) combine with γ chains to produce Hb Portland (ζ2/γ2) and with ε chains to produce Hb Gower-1 (ζ2/ε2).

Subsequently, when α chains are produced, they form Hb Gower-2, pairing with ε chains (α2/ε2). Fetal Hb is composed of α2/γ2 and the primary adult Hb (Hb A) of α2/β2. A third physiologic Hb, known as Hb A2, is formed by α2/δ2 chains, as in the image below.

Alpha chain genes in duplication on chromosome 16 Alpha chain genes in duplication on chromosome 16 pairing with non-alpha chains to produce various normal hemoglobins.

Genetic changes

All the genes that control the production of globin chains lie within 1 of 2 clusters located on 2 different chromosomes. Chromosome 11 is the site of 5 functional b-like globin genes arranged in a link cluster over 60 kilobases (kb). From left to right (5'-3'), they are ε/γ-G/γ-A/δ/β. γ-G and γ-A differ by only one amino acid (alanine vs glycine).

A critical control region of the d-globin gene (promoter) is known to be defective; it inhibits messenger RNA (mRNA) processing, resulting in only a small amount of Hb A2 (α2/δ2) production, which thus accounts for less than 3% of total Hb in adult RBCs.

The α-like globin gene cluster is located on chromosome 16 and consists of 3 functional genes. From left to right (5'-3'), the genes are α/α2/α1.

Understanding the structure of the globin genes, how they are regulated to produce globin chains, and how the chains pair together to produce the various Hbs is critical for appreciating the different pathologic changes of this process that result in thalassemia.

Molecular biology

Each globin gene consists of a string of nucleotide bases divided into 3 coding sequences, termed exons, and 2 noncoding regions, known as introns or intervening sequences (IVS). See the image below.

Alpha and beta globin genes (chromosomes 16 and 11 Alpha and beta globin genes (chromosomes 16 and 11, respectively).

Three other regions, known as regulatory regions, are also present in the 5' noncoding or flanking region of each globin gene.

The first is the promoter, which plays a major role in the transcription of the structural genes. The second region is the enhancer, which has an important role in promoting erythroid-specific gene expression, as well as in coordinating the changes in globin gene activity at different stages of development (embryonal, fetal, adult). Enhancers can influence gene expression, despite being located some distance away from the gene itself, and, unlike the promoter, they can stimulate transcription irrespective of their orientation relative to the transcription start site. Finally, master regulatory sequences, known as locus control regions (in the β-globin gene family) and HS40 (in the α gene complex), are responsible for activating the genes in erythroid cells.

Each of these regulatory sequences has a modular structure that consists of short nucleotide motifs that act as binding sites for transcriptional activator or suppressor molecules. Such molecules activate or suppress gene expression in different cell types at different stages of development. A certain gene is transcribed by an initiation complex formed of certain proteins and a number of transcription factors, which interact with binding sites on the promoters and other regulatory sequences of the relevant genes.

When a gene is transcribed, mRNA is synthesized from one of the gene's DNA strands by the action of RNA polymerase. The initial product is a large mRNA precursor. Both exons and introns are initially present on this mRNA precursor; the introns are ultimately subsequently eliminated, and the exons are spliced together in the nucleus. At this stage, the mRNA, which has also been modified at both 5' and 3' ends, moves to the cytoplasm to act as a template for the production of globin chains.

Carrier molecules (transfer RNA [tRNA]) transport amino acids to the mRNA template. Each amino acid has a specific tRNA, which also contains 3 bases (anticodon), complimentary to the mRNA codons for that amino acid. The position of each amino acid in the globin chain is thus established by its corresponding triplet code (codon) in the globin gene. The cytidine, uridine, and guanosine (CUG) codon, for example, encodes the amino acid leucine, while the adenosine, adenosine, and adenosine (AAA) codon encodes lysine. When a tRNA molecule carries the initial amino acid to the template, directed by codon-anticodon base pairing, globin chain synthesis begins.

Once the first tRNA is in place, a complex is formed between several protein initiation factors and the subunit of the ribosome that is to hold the growing peptide chains together on the mRNA as it is translated. A second tRNA moves in alongside, and a new amino acid is bound to the first with a peptide bond, resulting in a peptide chain 2 amino acids long. This process continues from left to right until a specific codon for termination is reached. At this point, the completed peptide chain drops off the ribosome-mRNA complex and the ribosomal subunits are recycled. The globin chain is now ready to join a heme molecule and 3 other globin chains to form an Hb molecule.

The developmental switches from embryonic to fetal and then to adult Hb production are synchronized throughout the different organs of hematopoiesis (yolk sack, liver, bone marrow), which function at various stages of development. Even though the mechanism of such switches is not clearly understood, the globin gene promoter is known to contain information that specifies developmental stages of transcription.

Molecular pathology

To date, more than 1000 inherited mutations that affect either the structure or synthesis of the α- and β-globin chains are known. Mutations that result in β or α thalassemia are similar in principle but different in their patterns. Presently, more than 200 molecular defects known to downregulate the expression of β globin have been characterized. Such defects result in various types of β thalassemia.

Major deletions in β thalassemia are unusual (in contrast to α thalassemia), and most of the encountered mutations are single base changes, small deletions, or insertions of 1-2 bases at a critical site along the gene, as in the image below.

Various mutations in the beta gene that result in Various mutations in the beta gene that result in beta thalassemia.

These mutations occur in both exons and introns. For example, in a nonsense mutation, a single base change in the exon generates a stop codon in the coding region of the mRNA, resulting in premature termination of globin chain synthesis. This termination leads to the production of short, nonviable β chains.

Conversely, in the frame shift mutation, one or more bases on the exon are lost or inserted, resulting in a change in the reading frame of the genetic code or the production of a new stop codon.

RNA-splicing mutations are fairly common and represent a large portion of all mutations that result in β thalassemia. These mutations corrupt the splicing process. The importance of precise splicing in the quantitative production of stable functional mRNA cannot be overemphasized.

Slippage by even one nucleotide changes the reading frame of the mRNA. Both ends of the RNA introns (at the junction with the exons) have specific consensus sequences; these motifs include GT in the 5' (left end or donor site) consensus sequence and AG in the 3' (right end or acceptor site) consensus sequence. Such sequences are obligatory for correct splicing, and a single substitution at the invariant GT or AG sequence prevents splicing altogether and results in β-0 or α-0 thalassemia. Mutations in the other members of the consensus sequences, although still highly conserved, result in variable degrees of ineffective β-globin production, causing milder types of β thalassemia.

Mutations in exon sequences may activate a cryptic splice site. For example, in exon 1 of the β-globin gene, a consensus sequence that resembles a sequence in IVS-1 has been identified as the site for several distinct mutations, resulting in a gene that carries the features of both thalassemia and hemoglobinopathy simultaneously (quantitatively and qualitatively abnormal Hb production). This type of mutation represents a clear link between the thalassemias and the hemoglobinopathies, and, accordingly, these are labeled thalassemic hemoglobinopathies.

Thus, mutations at codon 19 (A to G), 26 (G to A), and 27 (G to T)—all in exon 1—result in reduced production of mRNA (thalassemia) because of inefficient splicing and an amino acid substitution encoded by the mRNA that is spliced and translated (albeit inefficiently) into protein. The resulting abnormal Hbs are Malay, E, and Knossos, respectively.

The flanking regions of the β-globin gene are also sites for various mutations. A single base substitution that involves the promoter element, for example, can downregulate β-globin gene transcription, resulting in a mild form of β thalassemia. Conversely, a mutation that affects the 3' end of the β-globin mRNA can interfere with its processing, resulting in a severe form of β thalassemia.

Clearly, many different β thalassemia mutations exist, and compound heterozygosity is frequently encountered. The resulting laboratory findings may lead to confusion. An example is the patient who manifests symptoms of β thalassemia major without an elevated Hb A2 level. The explanation for such a situation is often co-inheritance of β and δ thalassemia. δ/β thalassemia further is divided into δ/β+ or δ/β-0.

In the first type, a misalignment in the δ/β genes during meiosis results in the production of fused δ/β genes, a process responsible for the production of an Hb variant termed Hb Lepore.

The fused δ/β gene is under the control of a δ-globin gene promoter region (the β gene promoter is deleted in the process). Because the δ gene promoter carries mutations that lead to ineffective transcription, the fused δ/β chains are produced in limited amounts, resulting in thalassemia. This is in addition to the hemoglobinopathy.

Conversely, in d/β-0 thalassemia, a large deletion occurs in the β-globin gene cluster, removing both the δ and the β genes, which can also extend to involve all globin genes on chromosome 11, thus producing ε, γ, δ, and β-0 thalassemia.

Cellular pathophysiology

The basic defect in all types of thalassemia is imbalanced globin chain synthesis. However, the consequences of accumulation of the excessive globin chains in the various types of thalassemia are different. In β thalassemia, excessive α chains, unable to form Hb tetramers, precipitate in the RBC precursors and, in one way or another, produce most of the manifestations encountered in all of the β thalassemia syndromes; this is not the situation in α thalassemia.

The excessive chains in α thalassemia are γ chains earlier in life and β chains later in life. Because such chains are relatively soluble, they are able to form homotetramers that, although relatively unstable, nevertheless remain viable and able to produce soluble Hb molecules such as Hb Bart (4 γ chains) and Hb H (4 β chains). These basic differences in the 2 main types of thalassemia are responsible for the major differences in their clinical manifestations and severity.

α chains that accumulate in the RBC precursors are insoluble, precipitate in the cell, interact with the membrane (causing significant damage), and interfere with cell division. This leads to excessive intramedullary destruction of the RBC precursors. In addition, the surviving cells that arrive in the peripheral blood with intracellular inclusion bodies (excess chains) are subject to hemolysis; this means that both hemolysis and ineffective erythropoiesis cause anemia in the person with β thalassemia.

The ability of some RBCs to maintain the production of γ chains, which are capable of pairing with some of the excessive α chains to produce Hb F, is advantageous. Binding some of the excess a chains undoubtedly reduces the symptoms of the disease and provides additional Hb with oxygen-carrying ability.

Furthermore, increased production of Hb F, in response to severe anemia, adds another mechanism to protect the RBCs in persons with β thalassemia. The elevated Hb F level increases oxygen affinity, leading to hypoxia, which, together with the profound anemia, stimulates the production of erythropoietin. As a result, severe expansion of the ineffective erythroid mass leads to severe bone expansion and deformities. Both iron absorption and metabolic rate increase, adding more symptoms to the clinical and laboratory manifestations of the disease. The large numbers of abnormal RBCs processed by the spleen, together with its hematopoietic response to the anemia if untreated, results in massive splenomegaly, leading to manifestations of hypersplenism.

If the chronic anemia in these patients is corrected with regular blood transfusions, the severe expansion of the ineffective marrow is reversed. Adding a second source of iron would theoretically result in more harm to the patient. However, this is not the case because iron absorption is regulated by 2 major factors: ineffective erythropoiesis and iron status in the patient.

Ineffective erythropoiesis results in increased absorption of iron because of downregulation of the HAMP gene, which produces a liver hormone called hepcidin. Hepcidin regulates dietary iron absorption, plasma iron concentration, and tissue iron distribution and is the major regulator of iron. It acts by causing degradation of its receptor, the cellular iron exporter ferroportin. When ferroportin is degraded, it decreases iron flow into the plasma from the gut, from macrophages, and from hepatocytes, leading to a low plasma iron concentration. In severe hepcidin deficiency, iron absorption is increased and macrophages are usually iron depleted, such as is observed in patients with thalassemia intermedia.

Malfunctions of the hepcidin-ferroportin axis contribute to the etiology of different anemias, such as is seen in thalassemia, anemia of inflammation, and chronic renal diseases. Improvement and availability of hepcidin assays facilitates diagnosis of such conditions. The development of hepcidin agonists and antagonists may enhance the treatment of such anemias.[6]

By administering blood transfusions, the ineffective erythropoiesis is reversed, and the hepcidin level is increased; thus, iron absorption is decreased and macrophages retain iron.

Iron status is another important factor that influences iron absorption. In patients with iron overload (eg, hemochromatosis), the iron absorption decreases because of an increased hepcidin level. However, this is not the case in patients with severe β thalassemia because a putative plasma factor overrides such mechanisms and prevents the production of hepcidin. Thus, iron absorption continues despite the iron overload status.

As mentioned above, the effect of hepcidin on iron recycling is carried through its receptor "ferroportin," which exports iron from enterocytes and macrophages to the plasma and exports iron from the placenta to the fetus. Ferroportin is upregulated by iron stores and downregulated by hepcidin. This relationship may also explain why patients with β thalassemia who have similar iron loads have different ferritin levels based on whether or not they receive regular blood transfusions.

For example, patients with β thalassemia intermedia who are not receiving blood transfusions have lower ferritin levels than those with β thalassemia major who are receiving regular transfusion regimens, despite a similar iron overload. In the latter group, hepcidin allows recycling of the iron from the macrophages, releasing high amounts of ferritin. In patients with β thalassemia intermedia, in whom the macrophages are depleted despite iron overload, lower amounts of ferritin are released, resulting in a lower ferritin level.

Most nonheme iron in healthy individuals is bound tightly to its carrier protein, transferrin. In iron overload conditions, such as severe thalassemia, the transferrin becomes saturated, and free iron is found in the plasma. This iron is harmful since it provides the material for the production of hydroxyl radicals and additionally accumulates in various organs, such as the heart, endocrine glands, and liver, resulting in significant damage to these organs.

By understanding the etiology of the symptoms in thalassemia, one can appreciate that certain modifiers may result in the development of milder types of thalassemia. Factors that may reduce the degree of globin chain imbalance are expected to modify the severity of the symptoms; co-inheritance of α thalassemia, the presence of higher Hb F level, or the presence of a milder thalassemia mutation all typically ameliorate the symptoms of thalassemia.

Malaria hypothesis

In 1949, Haldane suggested a selective advantage for survival in individuals with the thalassemia trait in regions where malaria is endemic. He argued that lethal RBC disorders such as thalassemia, sickle cell disease, and G-6-PD deficiency are present almost exclusively in tropical and subtropical regions of the world. The incidence of these genetic mutations in a certain population thus reflects the balance between the premature death of homozygotes and the increased fitness of heterozygotes.

For instance, in β thalassemia, the frequency of the gene is greater than 1% in the Mediterranean Basin, India, Southeast Asia, North Africa, and Indonesia; it is very uncommon in other parts of the world. α thalassemia may be the most common single gene disorder in the world (5-10% in the Mediterranean, 20-30% in West Africa, approximately 68% in the South Pacific); however, the gene prevalence in Northern Europe and Japan is less than 1%.

The mechanism of protection against malaria is not clear. Hb F in cells has been demonstrated to retard the growth of the malaria parasite, and, by virtue of its high level in infants with β thalassemia trait, the fatal cerebral malaria known to kill infants in these areas may be prevented. The RBCs of patients with Hb H disease have also shown a suppressive effect on the growth of the parasites. This effect is not observed in α thalassemia trait.

Classification of thalassemia

A large number of thalassemic syndromes are currently known; each involves decreased production of one globin chain or more, which form the different Hbs normally found in RBCs. The most important types in clinical practice are those that affect either α or β chain synthesis.

α thalassemia

Several forms of α thalassemia are known in clinical practice. The most common forms are as follows:

  • Silent carrier α thalassemia

    • This is a fairly common type of subclinical thalassemia, usually found by chance among various ethnic populations, particularly African American, while the child is being evaluated for some other condition. As pointed out above, 2 α genes are located on each chromosome 16, giving α thalassemia the unique feature of gene duplication, see the image below. This duplication is in contrast to only one β-globin gene on chromosome 11.

      Alpha and beta globin genes (chromosomes 16 and 11 Alpha and beta globin genes (chromosomes 16 and 11, respectively).
    • In the silent carrier state, one of the α genes is usually absent, leaving only 3 of 4 genes (aa/ao). Patients are hematologically healthy, except for occasional low RBC indices.

    • In this form, the diagnosis cannot be confirmed based on Hb electrophoresis results, which are usually normal in all α thalassemia traits. More sophisticated tests are necessary to confirm the diagnosis. One may look for hematologic abnormalities in family members (eg, parents) to support the diagnosis. A CBC count in one parent that demonstrates hypochromia and microcytosis in the absence of any explanation is frequently adequate evidence for the presence of thalassemia.

  • α thalassemia trait: This trait is characterized by mild anemia and low RBC indices. This condition is typically caused by the deletion of 2 α (a) genes on one chromosome 16 (aa/oo) or one from each chromosome (ao/ao). This condition is encountered mainly in Southeast Asia, the Indian subcontinent, and some parts of the Middle East. The ao/ao form is much more common in black populations because the doubly deleted (oo) form of chromosome 16 is rare in this ethnic group.

  • Hb H disease: This condition, which results from the deletion or inactivation of 3 α globin genes (oo/ao), represents α thalassemia intermedia, with mildly to moderately severe anemia, splenomegaly, icterus, and abnormal RBC indices. When peripheral blood films stained with supravital stain or reticulocyte preparations are examined, unique inclusions in the RBCs are usually observed. These inclusions represent b chain tetramers (Hb H), which are unstable and precipitate in the RBC, giving it the appearance of a golf ball. These inclusions are termed Heinz bodies, depicted below.

    Supra vital stain in hemoglobin H disease that rev Supra vital stain in hemoglobin H disease that reveals Heinz bodies (golf ball appearance).
  • α thalassemia major: This condition is the result of complete deletion of the a gene cluster on both copies of chromosome 16 (oo/oo), leading to the severe form of homozygous α thalassemia, which is usually incompatible with life and results in hydrops fetalis unless intrauterine blood transfusion is given.

β thalassemia

Similar to α thalassemia, several clinical forms of β thalassemia are recognized; some of the more common forms are as follows:

  • Silent carrier β thalassemia: Similar to patients who silently carry α thalassemia, these patients have no symptoms, except for possible low RBC indices. The mutation that causes the thalassemia is very mild and represents a β+ thalassemia.

  • β thalassemia trait: Patients have mild anemia, abnormal RBC indices, and abnormal Hb electrophoresis results with elevated levels of Hb A2, Hb F, or both. Peripheral blood film examination usually reveals marked hypochromia and microcytosis (without the anisocytosis usually encountered in iron deficiency anemia), target cells, and faint basophilic stippling, as depicted below. The production of β chains from the abnormal allele varies from complete absence to variable degrees of deficiency.

    Peripheral blood film in thalassemia minor. Peripheral blood film in thalassemia minor.
  • Thalassemia intermedia: This condition is usually due to a compound heterozygous state, resulting in anemia of intermediate severity, which typically does not require regular blood transfusions.

  • β thalassemia associated with β chain structural variants: The most significant condition in this group of thalassemic syndromes is the Hb E/β thalassemia, which may vary in its clinical severity from as mild as thalassemia intermedia to as severe as β thalassemia major.

  • Thalassemia major (Cooley anemia): This condition is characterized by transfusion-dependent anemia, massive splenomegaly, bone deformities, growth retardation, and peculiar facies in untreated individuals, 80% of whom die within the first 5 years of life from complications of anemia. Examination of a peripheral blood preparation in such patients reveals severe hypochromia and microcytosis, marked anisocytosis, fragmented RBCs, hypochromic macrocytes, polychromasia, nucleated RBCs, and, on occasion, immature leukocytes, as shown below.

    Peripheral blood film in Cooley anemia. Peripheral blood film in Cooley anemia.

Frequency

United States

Because of immigration to the United States from all parts of the world and the intermarriages that have taken place over the years, all types of thalassemia occur in any given part of the country. However, until recently, the number of patients with severe forms of both β and α thalassemia has been very limited. For this reason, finding more than 2-5 patients with the very severe forms in any pediatric hematology center is unusual (except for in the few referral centers in the United States).

However, this situation is changing rapidly in certain parts of the country. In the last 10 years, Asian immigration has been steadily increasing. According to the Federal Census Bureau, in 1990, 6.9 million Asians were in the United States, twice that reported in the 1980 Census count. The prevalence of various thalassemia syndromes in this population is very high. β and α thalassemia, as well as Hb E/β thalassemia, are currently on the rise in the state of California as a result of the large concentration of Asian immigrants in that part of the country.

The interaction between Hb E (a β chain variant) and β thalassemia (both very common among Southeast Asians) has created the Hb E/β thalassemia entity, which is now believed to be the most common thalassemia disorder in many regions of the world, including coastal North America, thus replacing β thalassemia major in frequency. For this reason, the cord-blood screening program for detection of hemoglobinopathy in California has been modified to include the detection of Hb H disease. In California alone, 10-14 new cases of β thalassemia major and Hb E/β thalassemia and 40 cases of neonatal Hb H disease are detected annually.

International

Worldwide, 15 million people have clinically apparent thalassemic disorders. Reportedly, disorders worldwide, and people who carry thalassemia in India alone number approximately 30 million. These facts confirm that thalassemias are among the most common genetic disorders in humans; they are encountered among all ethnic groups and in almost every country around the world.

Certain types of thalassemia are more common in specific parts of the world. β thalassemia is much more common in Mediterranean countries such as Greece, Italy, and Spain. Many Mediterranean islands, including Cyprus, Sardinia, and Malta, have a significantly high incidence of severe β thalassemia, constituting a major public health problem. For instance, in Cyprus, 1 in 7 individuals carries the gene, which translates into 1 in 49 marriages between carriers and 1 in 158 newborns expected to have β thalassemia major. As a result, preventive measures established and enforced by public health authorities have been very effective in decreasing the incidence among their populations. β thalassemia is also common in North Africa, the Middle East, India, and Eastern Europe. Conversely, α thalassemia is more common in Southeast Asia, India, the Middle East, and Africa.

A literature review by Lai et al indicated that α thalassemia, β thalassemia, and α + β thalassemia have an overall prevalence in mainland China of 7.88%, 2.21%, and 0.48%, respectively (although most of the data were collected from southern China).[7]

Mortality/Morbidity

α thalassemia major is a mortal disease, and virtually all affected fetuses are born with hydrops fetalis as a result of severe anemia. Several reports describe newborns with α thalassemia major who survived after receiving intrauterine blood transfusions. Such patients require extensive medical care thereafter, including regular blood transfusions and chelation therapy, similar to patients with β thalassemia major. Morbidity and mortality remain high among such patients. In the rare reports of newborns with α thalassemia major born without hydrops fetalis who survived without intrauterine transfusion, high level of Hb Portland, which is a normally functioning embryonic Hb, is thought to be the cause for the unusual clinical course.

Patients with Hb H disease also require close monitoring. They may require frequent or only occasional blood transfusions, depending on the severity of the condition. Some patients may require splenectomy. Morbidity is usually related to the anemia, complications of blood transfusions, massive splenomegaly in some patients, or the complications of splenectomy in others.

In patients with various types of β thalassemia, mortality and morbidity vary according to the severity of the disease and the quality of care provided.[8, 9, 10] Severe cases of β thalassemia major are fatal if not treated. Heart failure due to severe anemia or iron overload is a common cause of death in affected persons. Liver disease, fulminating infection, or other complications precipitated by the disease or by its treatment are some of the causes of morbidity and mortality in the severe forms of thalassemia.[11]

Morbidity and mortality are not limited to untreated persons; those receiving well-designed treatment regimens also may be susceptible to the various complications of the disease. Organ damage due to iron overload, chronic serious infections precipitated by blood transfusions, or complications of chelation therapy, such as cataracts, deafness, or infections with unusual microorganisms (eg, Yersinia enterocolitica), are all considered potential complications.

Race

Although thalassemia occurs in all races and ethnic groups, certain types of thalassemia are more common in some ethnic groups than in others (see Frequency). β thalassemia is common in southern Europe, the Middle East, India, and Africa. α thalassemia is more common in Southeast Asia; nevertheless, it is also seen in other parts of the world. Furthermore, specific mutations of the same type of thalassemia are more common among certain ethnic groups than others; this facilitates the screening and diagnostic processes because certain probes for the more common mutations in a particular region are usually readily available.

The α thalassemia trait in Africa is usually not of the cis deletion on chromosome 16, unlike the condition in Southeast Asia, which is associated with complete absence of the α gene on one chromosome. When both parents have the cis deletion, the fetus may develop hydrops fetalis. For this reason, hydrops fetalis is not a risk in the African population, although it remains a risk for Southeast Asian population.

Sex

Both sexes are equally affected with thalassemia.

Age

Despite thalassemia's inherited nature, age at onset of symptoms varies significantly. In α thalassemia, clinical abnormalities in patients with severe cases and hematologic findings in carriers are evident at birth. Unexplained hypochromia and microcytosis in a neonate, depicted below, are highly suggestive of the diagnosis.

Peripheral blood film in hemoglobin H disease in a Peripheral blood film in hemoglobin H disease in a newborn.

However, in the severe forms of β thalassemia, symptoms may not be evident until the second half of the first year of life; until that time, the production of γ-globin chains and their incorporation into fetal Hb can mask the condition.

Milder forms of thalassemia are frequently discovered by chance and at various ages. Many patients with an apparent homozygous β thalassemia condition (ie, hypochromasia, microcytosis, electrophoresis negative for Hb A, evidence that both parents are affected) may show no significant symptoms or anemia for several years. Almost all such patients' conditions are categorized as β thalassemia intermedia during the course of their disease. This situation usually results when the patient has a milder form of the mutation, is a compound heterozygote for β+ and β-0 thalassemia, or has other compound heterozygosity.

 

Presentation

History

The history in patients with thalassemia widely varies, depending on the severity of the condition and the age at the time of diagnosis.

  • In most patients with thalassemia traits, no unusual signs or symptoms are encountered.

  • Some patients, especially those with somewhat more severe forms of the disease, manifest some pallor and slight icteric discoloration of the sclerae with splenomegaly, leading to slight enlargement of the abdomen. An affected child's parents or caregivers may report these symptoms. However, some rare types of β thalassemia trait are caused by a unique mutation, resulting in truncated or elongated β chains, which combine abnormally with α chains, producing insoluble dimers or tetramers. The outcome of such insoluble products is a severe hemolytic process that needs to be managed like thalassemia intermedia or, in some cases, thalassemia major.

  • The diagnosis is usually suspected in children with an unexplained hypochromic and microcytic picture, especially those who belong to one of the ethnic groups at risk. For this reason, physicians should always inquire about the patient's ethnic background, family history of hematologic disorders, and dietary history.

  • Thalassemia should be considered in any child with hypochromic microcytic anemia that does not respond to iron supplementation.

  • In more severe forms, such as β thalassemia major, the symptoms vary from extremely debilitating in patients who are not receiving transfusions to mild and almost asymptomatic in those receiving regular transfusion regimens and closely monitored chelation therapy.

  • Children with β thalassemia major usually demonstrate none of the initial symptoms until the later part of the first year of life (when β chains are needed to pair with α chains to form hemoglobin (Hb) A, after γ chains production is turned off). However, in occasional children younger than 3-5 years, the condition may not be recognized because of the delay in cessation of Hb F production.

  • Patients with Hb E/β thalassemia may present with severe symptoms and a clinical course identical to that of patients with β thalassemia major. Alternatively, patients with Hb E/β thalassemia may run a mild course similar to that of patients with thalassemia intermedia or minor. This difference in severity has been described among siblings from the same parents. Some of the variation in severity can be explained based on the different genotypes, such as the type of β thalassemia gene present (ie, β+ or β-0), the co-inheritance of an α thalassemia gene, the high level of Hb F, or the presence of a modifying gene These changes are caused by massive expansion of the bone due to the ineffective erythroid production.

  • The ineffective erythropoiesis also creates a state of hypermetabolism associated with fever and failure to thrive.

  • Occasionally, gout due to hyperuricemia, as well as kidney stones, are seen more frequently as patients with thalassemia major are living longer. Chronic anemia and exposure to chelating agents were thought to be blamed for this complication.[12]

  • Iron overload is one of the major causes of morbidity in all patients with severe forms of thalassemia, regardless of whether they are regularly transfused.

    • In transfused patients, heavy iron turnover from transfused blood is usually the cause; in nontransfused patients, this complication is usually deferred until puberty (if the patient survives to that age).

    • Increased iron absorption is the cause in nontransfused patients, but the reason behind this phenomenon is not clear. Many believe that, despite the iron overload state in these patients and the increased iron deposits in the bone marrow, the requirement for iron to supply the overwhelming production of ineffective erythrocytes is tremendous, causing significant increases in GI absorption of iron.

    • Bleeding tendency, increased susceptibility to infection, and organ dysfunction are all associated with iron overload.

  • Poor growth in patients with thalassemia is due to multiple factors and affects patients with well-controlled disease as well as those with uncontrolled disease.

  • Patients may develop symptoms that suggest diabetes, thyroid disorder, or other endocrinopathy; these are rarely the presenting reports.

Physical

Patients with thalassemia minor rarely demonstrate any physical abnormalities. Because the anemia is never severe and, in most instances, the Hb level is not less than 9-10 g/dL, pallor and splenomegaly are rarely observed.

In patients with severe forms of thalassemia, the findings upon physical examination widely vary, depending on how well the disease is controlled. Findings include the following:

  • Children who are not receiving transfusions have a physical appearance so characteristic that an expert examiner can often make a spot diagnosis.

  • In Cooley's original 4 patients, the stigmata of severe untreated β thalassemia major included the following:

    • Severe anemia, with an Hb level of 3-7g/dL

    • Massive hepatosplenomegaly

    • Severe growth retardation

    • Bony deformities

  • These stigmata are typically not observed; instead, patients look healthy. Any complication they develop is usually due to adverse effects of the treatment (transfusion or chelation).

  • Bony abnormalities, such as frontal bossing, prominent facial bones, and dental malocclusion, are usually striking.

  • Severe pallor, slight to moderately severe jaundice, and marked hepatosplenomegaly are almost always present.

Complications of severe anemia are manifested as intolerance to exercise, heart murmur, or even signs of heart failure. Growth retardation is a common finding, even in patients whose disease is well controlled by chelation therapy. Patients with signs of iron overload may also demonstrate signs of endocrinopathy caused by iron deposits. Diabetes and thyroid or adrenal disorders have been described in these patients. In patients with severe anemia who are not receiving transfusion therapy, neuropathy or paralysis may result from compression of the spine or peripheral nerves by large extramedullary hematopoietic masses.

Causes

Thalassemias are inherited disorders caused by various gene mutations. The clinical expression and severity are subject to numerous factors that may either mask the condition or exaggerate the symptoms, leading to a more severe disease.

 

DDx

Diagnostic Considerations

The differential diagnoses of thalassemic states in general depend on the age of the child at the time of presentation, the type of thalassemia and its severity, and, in severe cases, whether it is treated and well controlled. Furthermore, the form of thalassemia then has to be identified once the thalassemic condition is suspected because of the numerous thalassemic conditions.

Congenital dyserythropoietic anemia is a condition that may mimic severe forms of thalassemia in children. A bone marrow examination, hemoglobin (Hb) electrophoresis, and other tests reveal the diagnosis. Diamond-Blackfan anemia may also resemble severe forms of thalassemia in young infants.

The α thalassemia trait is similar to the β thalassemia trait. Both traits should be differentiated from iron deficiency anemia, which is the most common cause of hypochromasia and microcytosis in children and should be excluded before considering thalassemia. A child with presumed iron deficiency anemia that has not responded to adequate iron treatment is a good candidate for thalassemia workup.

In β thalassemia, elevated levels of Hb A2, F, or both are usually helpful in confirming the diagnosis. However, in α thalassemia, the Hb electrophoresis results are usually normal; in this case, and in cases in which iron study results are also nondiagnostic, nonspecific tests may help to differentiate iron deficiency anemia or anemia of chronic inflammation from thalassemia. Free erythrocyte protoporphyrin (FEP) levels are usually elevated in patients with iron deficiency or anemia of chronic inflammation but not with thalassemia. The soluble transferrin receptors (sTfR) levels are high in patients with iron deficiency but not in those with anemia of chronic infection or thalassemia.

The process of differentiating thalassemia trait from iron deficiency anemia must include the patient's medical, developmental, nutritional, and family history and a review of the child's CBC count, with emphasis on the RBC indices. Proper interpretation of the CBC count may save the physician time and may save the patient from unnecessary further testing (see Laboratory Studies). The anemia in patients with thalassemia trait is usually mild; the Hb level is rarely, if ever, less than 9 g/dL, unless the cause of the anemia is multifactorial. The RBC count is almost always higher in patients with thalassemia than in those with iron deficiency anemia; in fact, it is frequently higher than the reported reference range for the age.

In thalassemia, the RBC indices, including the mean corpuscular volume (MCV) and mean corpuscular Hb (MCH), are both significantly low for an Hb level that is either normal or only slightly low. In addition, the RBC distribution width (RDW) is usually normal, reflecting the homogenous population of the RBCs in thalassemia, whereas iron deficiency anemia is known to be associated with anisocytosis. Compare the images below. A faint basophilic stippling may be seen in the RBCs of patients with thalassemia but not typically in those of patients with iron deficiency.

Peripheral blood film in thalassemia minor. Peripheral blood film in thalassemia minor.
Peripheral blood in iron deficiency anemia. Peripheral blood in iron deficiency anemia.

Many formulae have been introduced to help in differentiating thalassemia trait from iron deficiency. The most practical and easiest to remember is the Mentzer index, which divides the patient's MCV by the RBC count (MCV/RBC). A result of less than 13 usually suggests thalassemia trait, while a result greater than 13 is indicative of iron deficiency.

Confirmation by Hb electrophoresis in β thalassemia is essential before the patient and the family are counseled. The Mentzer index loses its value if the patient has a combination of thalassemia and iron deficiency. In such patients, Hb electrophoresis results may also be inaccurate and misleading, since iron deficiency suppresses production of all Hbs, including Hb A2. For this reason, the Hb A2 level does not rise and is typically normal in these patients, masking the diagnosis of β thalassemia. In such cases, Hb electrophoresis should be repeated after the iron deficiency has been treated to obtain an accurate Hb A2 fraction.

When β and α thalassemia coexist, the elevated levels of Hb A2 and Hb F usually present in β thalassemia may also be lost. Furthermore, α thalassemia ameliorates the severity of β thalassemia since the decrease in α chains results in less inclusions and, hence, less hemolysis.

However, the confirmation of β thalassemia is easier than that of the α trait. The Hb electrophoresis result is usually normal, and DNA testing or globin chain synthesis enumeration are the only studies that confirm the diagnosis. A moderately severe form of α thalassemia, which some consider equivalent to β thalassemia intermedia, is termed Hb H disease. The disease is characterized by moderately severe anemia, splenomegaly, some jaundice, and, possibly, some bone changes due to marrow expansion. In this form, Hb electrophoresis is diagnostic in revealing the abnormal Hb, which is unstable and may be detected on the supra vital stain as inclusions in the RBCs (Heinz bodies).

The severity of Hb H disease depends on the inherited mutation. Seventy-five percent of Hb H mutations are caused by deletions on chromosome 16, which are usually associated with the milder forms of Hb H. Nondeletional forms are usually associated with severe Hb H and require transfusion. The diagnosis of Hb H may be difficult to establish, since it is unstable and may go undetected. The β tetramers of Hb H are replaced by γ tetramers in the form of Hb Bart. Patients with Hb H disease usually have more than 20% Hb Bart at birth, a finding that has helped to identify 90% of the neonates with Hb H disease in the newborns screening program in California.

Hb Constant Spring (CS) is the most common nondeletional α thalassemia mutation associated with Hb H disease. The cells that contain Hb CS are usually overhydrated, which causes the loss of the traditional microcytosis seen in patients with thalassemia. Hb H/CS disease is more severe than Hb H disease, sometimes requiring splenectomy to improve the anemia, a procedure associated with a high rate of portal vein thrombosis.

Many clinical entities associated with splenomegaly and anemia, such as storage diseases, and other forms of chronic hemolytic anemias are to be considered in the differential diagnosis. The homozygous α thalassemia is not compatible with life (unless intrauterine blood transfusion is administered), and a baby with hydrops fetalis is usually delivered.

Other causes of immune and nonimmune hydrops fetalis are also to be differentiated from the hydrops fetalis of α thalassemia major, a condition that was rarely seen in the past since the mutation that predisposes to this condition is limited to the Southeast Asian population, not the African population.

Rare forms of α thalassemia are also described. Hb CS results from a specific mutation in the α thalassemia gene, leading to the production of elongated α chains. The clinical manifestations in the homozygous state are similar to those encountered in patients with Hb H disease; however, they differ in the electrophoretic pattern. γ tetramers that consist of Hb Bart replace the β tetramers of Hb H.

Thalassemia may also interact with other globin structural variants, whether they involve β, α, or other chains. In the β variants, Bs, Bc, and Be are some of the globin chain's most common mutations. For instance, the interaction of Bs with β thalassemia produces a condition associated with sickle cell disease. Conversely, when Bs (sickle trait gene) interacts with an α thalassemia gene, less Hb S is present in the RBCs than when only Bs is present. Such interactions modify the severity of each separate condition.

The incidence of Hb E/β thalassemia has increased considerably in the United States due to the immigration of individuals from Southeast Asia, where the incidence of both Hg E and β thalassemia is high (see Frequency). Clinically, the severe forms of Hb E/β thalassemia are similar to the transfusion-dependent β thalassemia major. For this reason, the diagnosis Hb E/β thalassemia should be considered in patients of Southeast Asian descent.

Other rare thalassemia variants include Hb Lepore and hereditary persistence of fetal Hb (HPFH).

Differential Diagnoses

 

Workup

Laboratory Studies

Laboratory studies in thalassemia include the following:

  • The CBC count and peripheral blood film examination results are usually sufficient to suspect the diagnosis. Hemoglobin (Hb) evaluation confirms the diagnosis in β thalassemia, Hb H disease, and Hb E/β thalassemia.

    • In the severe forms of thalassemia, the Hb level ranges from 2-8 g/dL.

    • Mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) are significantly low, but, unlike thalassemia trait, thalassemia major is associated with a markedly elevated RDW, reflecting the extreme anisocytosis.

    • The WBC count is usually elevated in β thalassemia major; this is due, in part, to miscounting the many nucleated RBCs as leukocytes. Leukocytosis is usually present, even after excluding the nucleated RBCs. A shift to the left is also encountered, reflecting the hemolytic process.

    • Platelet count is usually normal, unless the spleen is markedly enlarged.

    • Peripheral blood film examination reveals marked hypochromasia and microcytosis, hypochromic macrocytes that represent the polychromatophilic cells, nucleated RBCs, basophilic stippling, and occasional immature leukocytes, as shown below.

      Peripheral blood film in Cooley anemia. Peripheral blood film in Cooley anemia.
    • Contrast this with the abnormalities associated with Hb H, an α thalassemia, shown below.

      Supra vital stain in hemoglobin H disease that rev Supra vital stain in hemoglobin H disease that reveals Heinz bodies (golf ball appearance).
    • Hb electrophoresis usually reveals an elevated Hb F fraction, which is distributed heterogeneously in the RBCs of patients with β thalassemia, Hb H in patients with Hb H disease, and Hb Bart in newborns with α thalassemia trait. In β -0 thalassemia, no Hb A is usually present; only Hb A2 and Hb F are found.

  • Iron studies are as follows:

    • Serum iron level is elevated, with saturation reaching as high as 80%.

    • The serum ferritin level, which is frequently used to monitor the status of iron overload, is also elevated. However, an assessment using serum ferritin levels may underestimate the iron concentration in the liver of a transfusion-independent patient with thalassemia.

  • Complete RBC phenotype, hepatitis screen, folic acid level, and human leukocyte antigen (HLA) typing are recommended before initiation of blood transfusion therapy.

Imaging Studies

Skeletal survey and other imaging studies reveal classic changes of the bones that are usually encountered in patients who are not regularly transfused.

The striking expansion of the erythroid marrow widens the marrow spaces, thinning the cortex and causing osteoporosis. These changes, which result from the expanding marrow spaces, usually disappear when marrow activity is halted by regular transfusions. Osteoporosis and osteopenia may cause fractures, even in patients whose conditions are well-controlled.

In addition to the classic "hair on end" appearance of the skull, shown below, which results from widening of the diploic spaces and observed on plain radiographs, the maxilla may overgrow, which results in maxillary overbite, prominence of the upper incisors, and separation of the orbit. These changes contribute to the classic "chipmunk" facies observed in patients with thalassemia major

The classic "hair on end" appearance on plain skul The classic "hair on end" appearance on plain skull radiographs of a patient with Cooley anemia.

Other bony structures, such as ribs, long bones, and flat bones, may also be sites of major deformities. Plain radiographs of the long bones may reveal a lacy trabecular pattern. Changes in the pelvis, skull, and spine become more evident during the second decade of life, when the marrow in the peripheral bones becomes inactive while more activity occurs in the central bones.

Compression fractures and paravertebral expansion of extramedullary masses, which could behave clinically like tumors, more frequently occur during the second decade of life. In a recent study from Thailand, investigating unrecognized vertebral fractures in adolescents and young adults with thalassemia syndrome, 13% of the patients studied were found to have fractures and 30% of them had multiple vertebral fractures. Those who were thought to be older had more severe disease, were splenectomized, and had been on chelation therapy for a longer time.[13]

MRI and CT scanning are usually used in diagnosing such complications. Chest radiography is used to evaluate cardiac size and shape. MRI and CT scanning can be used as noninvasive means to evaluate the amount of iron in the liver in patients receiving chelation therapy.

A newer non invasive procedure involves measuring the cardiac T2* with cardiac magnetic resonance (CMR). This procedure has shown decreased values in cardiac T2* due to iron deposit in the heart. Unlike liver MRI, which usually correlates very well with the iron concentration in the liver measured using percutaneous liver biopsy samples and the serum ferritin level, CMR does not correlate well with the ferritin level, the liver iron level, or echocardiography findings. This suggests that cardiac iron overload cannot be estimated with these surrogate measurements. This is also true in measuring the response to chelation therapy in patients with iron overload. The liver is clear of iron loading much earlier than the heart, which also suggests that deciding when to stop or reduce treatment based on liver iron levels is misleading.

The relationship between hepatic and myocardial iron concentration was assessed by T2-MRI in patients receiving chronic transfusion.[14] A poor correlation was noted, and approximately 14% of patients with cardiac iron overload were identified who had no matched degree of hepatic hemosiderosis. Left ventricular ejection fraction (LVEF) was insensitive for detecting high myocardial iron. For this reason, cardiac evaluation should be addressed separately.

T2* MRI technique (T2* is the time needed for the organ to lose two thirds of its signal, and it is measured in milliseconds (ms); when iron concentrate increases, T2* shortens). R2* is the reciprocal of T2* and equals 1000/T2* and is measured in a unit of inverse seconds. This technique has been recently validated and is used for evaluation of cardiac and liver iron load. A shortening of myocardial T2* to shorter than 20 ms is associated with an increased likelihood of decreased LVEF, whereas patients with T2 value of longer than 20 ms have a very low likelihood of decreased LVEF; values from 10-20 ms indicate a 10% chance of decreased LVEF, 8-10 ms an 18% chance, 6 ms a 38% chance, and 4 ms a 70% chance of decreased LVEF.[2]

This T2* MRI technique. is not readily available in many parts of the world. For this reason, the need for simpler and more available procedure was addressed in a study conducted recently in Italy, where serial echocardiographic LVEF measurements were proved to be very accurate and reproducible. The study suggested that a reduction in of LVEF greater than 7% , over time, as determined by 2-dimensional echocardiography, may be considered a strong predictive tool for the detection of thalassemia major patients with increased risk of cardiac death.[15]

Hepatic iron content (HIC) obtained by liver biopsy, cardiac function tests obtained by echocardiography measurements, and multiple-gated acquisition scan (MUGA) findings were compared with the results of iron measurements on R2-MRI in the liver and heart.[16]

Various iron overload patients were involved in the study, which revealed that R2-MRI was strongly associated with HIC (weakly but significantly with ferritin level) and represents an excellent noninvasive method to evaluate iron overload in the liver and heart and to monitor response to chelation therapy. T2* and R2* MRI are preferred by many, however, because they allow measurements of both liver and cardiac iron at the same time.[2]

HIC should be measured annually if possible in all patients on long-term blood transfusion therapy. Normal HIC values are up to 1.8 mg Fe/g dry weight levels, while a level of up to 7 mg/g/dry weight seen in carriers of hemochromatosis was shown to be asymptomatic and without any adverse effects. High levels of greater than 15 mg/g/dry weight is consistent with significant iron deposition and is associated with progression to liver fibrosis. Nontransferrin-bound iron (NTBI) is usually elevated in the plasma at this level.[2]

Other Tests

The following tests may be indicated:

  • ECG and echocardiography are performed to monitor cardiac function.

  • HLA typing is performed for patients for whom bone marrow transplantation is considered.

  • Eye examinations, hearing tests, renal function tests, and frequent blood counts are required to monitor the effects of deferoxamine (DFO) therapy and the administration of other chelating agents (see Treatment, Medication).

Procedures

Bone marrow aspiration is needed in certain patients at the time of the initial diagnosis to exclude other conditions that may manifest as thalassemia major.

Liver biopsy is used to assess iron deposition and the degree of hemochromatosis. However, using liver iron content as a surrogate for evaluation of cardiac iron is misleading. Many studies have shown very poor correlation between the two; hence, cardiac evaluation for the presence of iron overload needs to be addressed separately.

Measurement of urinary excretion of iron after a challenge test of DFO is used to evaluate the need to initiate chelation therapy and reflects the amount of iron overload.

Histologic Findings

All severe forms of thalassemia exhibit hyperactive marrow with erythroid hyperplasia and increased iron stores in marrow, liver, and other organs. In the untreated person with severe disease, extramedullary hematopoiesis in unusual anatomic sites is one of the known complications.

Erythroid hyperplasia is observed in bone marrow specimens. Increased iron deposition is usually present in marrow, as depicted in the image below, liver, heart, and other tissues.

Excessive iron in a bone marrow preparation. Excessive iron in a bone marrow preparation.

Staging

Some use a relevant staging system based on the cumulative numbers of blood transfusions given to the patient to grade cardiac-related symptoms and determine when to start chelation therapy in patients with β thalassemia major or intermedia. In this system, patients are divided into 3 groups.

The first group contains those who have received fewer than 100 units of packed RBCs (PRBCs) and are considered to have stage I disease. These patients are usually asymptomatic; their echocardiograms reveal only slight left ventricular wall thickening, and both the radionuclide cineangiogram and the 24-hour ECG findings are normal.

Patients in the second group (stage II patients) have received 100-400 units of blood and may report slight fatigue. Their echocardiograms may demonstrate left ventricular wall thickening and dilatation but normal ejection fraction. The radionuclide cineangiogram findings are normal at rest but show no increase or fall in ejection fraction during exercise. Atrial and ventricular beats are usually noticed on the 24-hour ECG.

Finally, in stage III patients, symptoms range from palpitation to congestive heart failure, decreased ejection fraction on echocardiogram, and normal cineangiogram results or decreased ejection fraction at rest, which falls during exercise. The 24-hour ECG reveals atrial and ventricular premature beats, often in pairs or in runs.

A second classification, introduced by Lucarelli, is used for patients with severe disease who are candidates for hematopoietic stem cell transplantation (HSCT).[1] This classification is used to assess risk factors that predict outcome and prognosis and addresses 3 elements: (1) degree of hepatomegaly, (2) presence of portal fibrosis in liver biopsy sample, and (3) effectiveness of chelation therapy prior to transplantation.

If one of these elements is unfavorable prior to HSCT, the chance of event-free survival is significantly poorer than in patients who have neither hepatomegaly nor fibrosis and whose condition responds well to chelation (class 1 patients). The event-free survival rate after allogeneic HSCT for class 1 patients is 90%, compared with 56% for those with hepatomegaly and fibrosis and whose condition responds poorly to chelation (class 3).

 

Treatment

Surgical Care

Splenectomy is the principal surgical procedure used for many patients with thalassemia. The spleen is known to contain a large amount of the labile nontoxic iron (ie, storage function) derived from sequestration of the released iron. The spleen also increases RBC destruction and iron distribution (ie, scavenger function). These facts should always be considered before the decision is made to proceed with splenectomy. In addition, with recent reports of venous thromboembolic events (VTEs) after splenectomy, one should carefully consider the benefits and the risks before splenectomy is advocated. The spleen acts as a store for nontoxic iron, thereby protecting the rest of the body from this iron. Early removal of the spleen may be harmful (liver cirrhosis has occurred in such individuals).

In a retrospective study in which the charts and imaging studies of 89 patients with thalassemia intermedia were reviewed, renal stones were identified in 11 patients (12%) and 22 patients were on treatment for hyperuricemia (25%). The risk of renal stones seems to increase with age. Major identified risk factors for the formation of renal stones were splenectomy (91%) and higher number of erythroblasts. Such affected patients have higher mean creatinine levels and lower GFRs in comparison to nonaffected patients.[17]

Conversely, splenectomy is justified when the spleen becomes hyperactive, leading to excessive destruction of RBCs and thus increasing the need for frequent blood transfusions, resulting in more iron accumulation. Furthermore, if the labile iron pool in the spleen becomes the target for the action of the DFO (ie, removing the nonharmful pool and leaving the toxic one), splenectomy is further justified. The goal in this confusing dilemma should always be to achieve a negative iron balance, which, in many patients, has been possible by continuous administration of subcutaneous DFO.

Several criteria are used to aid in the decision for splenectomy; a practical one suggests that splenectomy may be beneficial in patients who require more than 200-250 mL/kg of PRBC per year to maintain an Hb level of 10 g/dL.

The risks associated with splenectomy are minimal, and many of the procedures are now performed by laparoscopy. Postsplenectomy risk of infections with encapsulated organisms and malaria in endemic areas is always a concern. The problem is minimal at the present time, since presplenectomy immunizations and postsurgical prophylactic antibiotics have significantly decreased the rates of such complications. Traditionally, the procedure is delayed whenever possible until the child is aged 4-5 years or older. Aggressive treatment with antibiotics should always be administered for any febrile illness while awaiting the results of cultures. Low-dose daily aspirin is also beneficial when the platelet count rises to more than 600,000/µL postsplenectomy.

Another surgical procedure in patients with severe thalassemia on transfusion therapy is the placement of a central line for the ease and convenience of administering blood transfusions, chelation therapy, or both.

Consultations

The following consultations may be indicated:

  • Pediatric surgeon

  • Pediatric endocrinologist

  • Pediatric ophthalmologist

  • Pediatric otolaryngologist

  • Pediatric gastroenterologist

  • Pediatric HSCT specialist

Diet

A normal diet is recommended, with emphasis on the following supplements: folic acid, small doses of ascorbic acid (vitamin C), and alpha-tocopherol (vitamin E). Iron should not be given, and foods rich in iron should be avoided. Drinking coffee or tea has been shown to help decrease absorption of iron in the gut.

In an animal study, green tea as antioxidant was shown to inhibit or delay the deposition of hepatic iron in thalassemic mice.[18] This prevented iron-induced free radical generation, which has been implicated in liver damage and fibrosis.

Activity

Patients with well-controlled disease are usually fully active. Patients with anemia, heart failure, or massive hepatosplenomegaly are usually restricted according to their tolerances.

 

Medication

Medication Summary

Medications needed for the treatment of various types of thalassemias are nonspecific and only supportive. A list of such medications is provided in this article.

Antipyretics, analgesics

Class Summary

Administration before blood transfusion prevents or decreases febrile reactions.

Acetaminophen (Tylenol, Tempra, Panadol)

Antipyretic effect through action on hypothalamic heat-regulating center. Action equal to that of aspirin but preferred because does not have adverse effects of aspirin.

Antihistamines

Class Summary

Administration prior to blood transfusion may decrease or prevent allergic reactions.

Diphenhydramine hydrochloride (Benadryl)

Antihistamine with anticholinergic and sedative effects.

Chelating agents

Class Summary

These agents are used to chelate excessive iron from the body in patients with iron overload.

Deferoxamine mesylate (Desferal)

Chelates iron from ferritin or hemosiderin but not from transferrin, cytochrome, or Hb.

Deferasirox (Exjade)

Deferasirox comes in tablet form for oral suspension. It is an oral iron chelation agent that reduces liver iron concentration and serum ferritin levels. Deferasirox binds to iron with a high affinity, in a 2:1 ratio. It is approved to treat chronic iron overload due to multiple blood transfusions and nontransfusion-dependent thalassemia.

Corticosteroids

Class Summary

Some patients may develop local reaction at the site of DFO injection. Hydrocortisone in the DFO solution may help to reduce the reaction.

Hydrocortisone (Solu-Cortef, Cortef, Hydrocortone)

Anti-inflammatory action. Both Na succinate (Solu-Cortef) and Na phosphate (Cortef) forms used for IV infusion, but not Na acetate form (Hydrocortone).

Antibacterial combinations

Class Summary

Certain antibacterial agents are known to be effective against organisms that often cause infection in patients with iron overload who also are receiving DFO therapy. Although rare in healthy patients, Y enterocolitica requires siderophores; thus, infections with this pathogen occur with relative frequency in patients with thalassemia. Appropriate therapy is a combination of trimethoprim-sulfamethoxazole (TMP/SMX) and gentamicin. Patients who require splenectomy need to receive prophylactic penicillin to prevent fulminating sepsis, especially those younger than 5 years. Many recommend that older patients receive prophylactic antibiotics for at least 3 years after splenectomy.

Trimethoprim-sulfamethoxazole (TMP/SMX, Bactrim, Septra)

In combination with gentamicin, DOC for infections by Y enterocolitica.

Gentamicin (Garamycin)

Aminoglycoside known to be effective against gram-negative microorganisms. Dosing regimens are numerous; adjust dose based on CrCl and changes in volume of distribution.

Penicillin V (Pen-Vee, Veetids, V-Cillin K)

DOC for postsplenectomy prophylaxis; erythromycin used in patients allergic to penicillin. Active against most microorganisms considered to be major offenders in splenectomized patients, namely, streptococcal, pneumococcal, and some staphylococcal microorganisms, but not penicillinase-producing species.

Vitamins

Class Summary

Several vitamins are required, as either supplements or enhancers of the chelating agent.

Serum level of vitamin C is low in patients with thalassemia major, likely due to increased consumption in the face of iron overload.

Ascorbic acid (Vitamin C, Cebid, Vita-C, Ce-Vi-Sol, Cecon, Dull-C)

Delays conversion of transferrin to hemosiderin, thus making iron more accessible to chelation.

Alpha-tocopherol (Vitamin E, Aquasol E, Vita-Plus E Softgels, Vitec, E-Vitamin)

An antioxidant. Prevents iron-mediated toxicity caused by peroxidation of cell membrane lipids, reducing extent of accompanying hemolysis. Protects polyunsaturated fatty acids in membranes from attack by free radicals and protects RBCs against hemolysis. Demonstrated to be deficient in patients with iron overload receiving chelation therapy.

Folic acid (Folvite)

Required for DNA synthesis; therefore in great demand in these patients because of increased cellular turnover. Deficient in most patients with chronic hemolysis.

Vaccines

Class Summary

Splenectomized patients are usually prone to developing infections with the encapsulated organisms such as pneumococci, Haemophilus influenzae, and meningococcal organisms. For this reason, such patients now are immunized against these organisms 1-2 wk prior to the procedure to prevent infections.

Pneumococcal vaccine polyvalent (Pneumovax)

Polyvalent polysaccharide vaccine (PS23) contains 23 serotypes that cause 70% of invasive infections. This vaccine should not be given to children < 2 y. In rare cases in which splenectomy is required in children < 2 y and no previous vaccination has been given, conjugate type (PCV7), which contains only 7 serotypes, is required.

Haemophilus influenza type b vaccine (ActHIB, HibTITER, PedvaxHIB)

Used for routine immunization of children against invasive diseases caused by H influenzae type b. Decreases nasopharyngeal colonization. The CDC's Advisory Committee on Immunization Practices (ACIP) recommends that all children receive one of the conjugate vaccines licensed for infant use beginning routinely at age 2 mo.

Conjugate form usually given in series of 3 doses at ages 2, 4, and 6 mo. Patients who have already received primary vaccine and booster dose at age 12 mo or older are usually protected and do not require further vaccination prior to splenectomy.

Meningitis group A C Y and W-135 vaccine (Menomune-A/C/Y/W-135)

Used only in children >2 y. Serogroup specific against groups A, C, Y, and W-135 Neisseria meningitidis.

Pneumococcal 7-valent conjugate vaccine (Prevnar)

Sterile solution of saccharides of capsular antigens of S pneumoniae serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F individually conjugated to diphtheria CRM197 protein. These 7 serotypes have been responsible for >80% of invasive pneumococcal disease in children < 6 y in the United States. Also accounted for 74% of penicillin-nonsusceptible S pneumoniae (PNSP) and 100% of pneumococci with high-level penicillin resistance. Customary age for first dose is 2 mo but can be given to infants as young as 6 wk. Preferred sites of IM injection are anterolateral aspect of the thigh in infants or deltoid muscle of upper arm in toddlers and young children. Do not inject vaccine in gluteal area or areas that may contain a major nerve trunk or blood vessel. A 3-dose series, 0.5 mL each, is initiated in infants aged 7-11 mo (4 wk apart; third dose after first birthday).

Children aged 12-23 mo are given 2 doses (2 mo apart). Children >24 mo through 9 y are given 1 dose. Minor illnesses, such as a mild upper respiratory tract infection, with or without low-grade fever, are not generally considered contraindications.

Antineoplastic agent

Class Summary

Some patients may respond to hydroxyurea and subsequently decrease or eliminate transfusion requirements. Patients with homozygous or heterozygous XmnI polymorphism were found to respond favorably in one study.[19] Improvement of pulmonary hypertension following hydroxyurea has also been observed.[20]

Hydroxyurea (Droxia, Hydrea)

Inhibitor of deoxynucleotide synthesis.

Growth Hormone

Class Summary

Excessive chelation with deferoxamine may cause growth retardation. Growth hormone may be effective in increasing growth rate in all thalassemic patient particularly the ones with growth hormone deficiency.[21]

Somatropin (Saizen, Genotropin, Humatrope, Norditropin, Tev-Tropin)

Human growth hormone produced by recombinant DNA technology (mouse C127 cell line). Elicits anabolic and anticatabolic influence on various cells including: myocytes, hepatocytes, adipocytes, lymphocytes, and hematopoietic cells. Exerts activity on specific cell receptors including insulinlike growth factor-1 (IGF-1).

 

Follow-up

Further Outpatient Care

Blood transfusions are usually given at scheduled outpatient visits. Patients must be scheduled for regular laboratory studies to monitor iron deposition status and hepatic, cardiac, and renal functions. Patients receiving deferoxamine (DFO) require annual visits to assess for visual and hearing disturbances. Echocardiography and ECG are used to monitor cardiac function.

Further Inpatient Care

Uncomplicated cases of thalassemia major are usually managed in an outpatient setting. Inpatient care is usually reserved for infectious complications, surgical procedures, or for the rare patient treated with hematopoietic stem cell transplantation (HSCT).

Inpatient & Outpatient Medications

See Medication above.

Deterrence/Prevention

Screening and prevention includes the following:[22]

  • In persons with β thalassemia trait, confirming the diagnosis is usually easy. In such situations, genetic counseling is necessary, and, if both parents are carriers, a detailed discussion with the couple should include all possible outcomes. These include the 1 in 4 chance of having a severely affected or completely healthy child and a 1 in 2 chance of having a child with heterozygous thalassemia.

  • For α thalassemia carriers, confirmation is not that simple. Hemoglobin (Hb) electrophoresis is usually not informative. For this reason, more sophisticated studies are warranted if confirmation is critical. Genetic counseling should be provided for patients with β thalassemia if a sibling or a family member is known to be affected.

  • Prenatal DNA testing has been available for several years. The decision to perform prenatal diagnosis in parents known to be at risk for having a child with thalassemia is complex and is usually influenced by several factors, such as religion, culture, education, and the number of children in the family. Genetic counseling by professionals that addresses the details of both the genetic risks and the testing risks involved is expected to help the parents make an informed and intelligent decision concerning the procedure. Unfortunately, such tests are not available in certain areas of the world where they are needed most. Extensive screening programs and prenatal diagnosis has resulted in a significant decline in the incidence of β thalassemia in some of the high-risk Mediterranean countries.

  • It is fortunate that several new methods for neonatal screening have recently evolved to replace the complex DNA sequencing, restriction enzyme polymerase chain reaction (RE-PCR), or the amplification refractory mutation system (ARMS). Such new methods include pyrosequencing, described as, "a more sensitive and rapid approach to fetal genotyping." It was used for 12 nondeletional common α- and β-globin gene mutations in the United Kingdom. This method was found to be 100% in concordance with the fetal diagnosis results obtained by ARMS-PCR or DNA sequencing. The test is a good choice for rapid and cost-effective prenatal diagnosis of thalassemia and sickle cell disease.[23]

  • In another study from Cyprus, a next-generation sequencing (NGS) of single-nucleotide polymorphism (SNPs) was introduced as a noninvasive prenatal diagnostic method. A modified version of NGS called "targeted sequencing" based on detection of paternally inherited fetal alleles in maternal plasma was used. Four SNPs located in the β-globin locus with a high degree of heterozygosity in the Cypriot population were selected as a target. The presence or absence of the paternal mutant allele was correctly determined in 27 of 34 samples analyzed, showing that NGS is effective in detecting paternally inherited alleles in the maternal plasma.[24]

  • Successful prevention programs in different parts of the world have resulted in an impressive decline in the number of patients with severe forms of thalassemia. Ferrara, Cyprus, Sardinia, Greece, and the United Kingdom were among the first to report a significant decline in the birth rate of children with thalassemia major. The Cypriot screening program continues to prove a great success, despite the false claim that it is a new form of eugenics.[25] Many other regions with more limited resources are following their steps with remarkable success.

  • In addition to the effective prenatal diagnosis adopted in the countries mentioned, other measures such as premarital screening programs, genetic counseling, and restrictions on issuing marriage certificates and licenses also proved to be effective. Because many of the countries where thalassemia prevails are poor and cannot afford sophisticated preventive programs, more practical approaches are clearly needed.

  • Screening of children, pregnant women, and individuals visiting public health facilities is effective in identifying individuals at risk who require further testing. A simple CBC count, with emphasis on the RBC counts and indices, including the mean corpuscular volume (MCV), mean corpuscular Hb (MCH), and RBC distribution width (RDW), is the main component of such screening processes. Persons suspected to be positive for thalassemia are checked for elevated levels of Hb A2, Hb F, or both for confirmation. In some situations, this simple method is not adequate, and further testing, including analyses of globin chain synthesis, must be performed to reach a final diagnosis.

Prenatal diagnosis includes the following:

  • Globin chain synthesis, which was once used in postnatal diagnosis, was also used on fetal cells obtained by fetoscopy to screen the fetus. This test reveals imbalanced production of certain globin chains that are diagnostic of thalassemia.

  • Since polymerase chain reaction (PCR) techniques have become available, several new methods are now in use to identify affected babies or carrier individuals accurately and quickly. The DNA material is obtained by chorionic villus sampling (CVS), and mutations that change restriction enzyme cutting sites can be identified.

  • Because many of the mutations that cause α and β thalassemia have become known in recent years, identifying such mutations on the amplified β-globin gene region is now possible with specific labeled oligonucleotide probes. Some of the new techniques can give accurate results in less than 3 hours.

  • Several publications have shown that prenatal diagnosis of thalassemia and hemoglobinopathies could be achieved by simple methods in routine setting. Capillary electrophoresis on fetal cells has proved to be reliable.[26] The same method has also been reported to have an advantage over other methods of Hb E evaluation because it could separate the peaks of Hb A2 from that of Hb E in patients with Hb E mutations.[27] In a study from Yi et al, PCR/ligase detection reaction (LDR) capillary electrophoresis assay for the detection of β thalassemia fetal mutation in maternal plasma was shown to be a noninvasive and highly sensitive procedure with good potential.[28]

Complications

Complications include the following:

  • Iron overload

    • Traditionally, ferritin level assessment has been the most commonly used test for indirect evaluation of body iron stores, even though it reflects only 1% of the total iron storage pool. The test is not perfect or accurate, as various conditions complicate the interpretation of its values. For this reason, reliance on serum ferritin assessment alone can lead to an inaccurate assessment of body iron stores in patients with iron overload who have been transfused heavily and who have levels in excess of the upper limit for the physiologic ferritin synthesis (400 mcg/L). At high levels, the test loses its clinical relevance since ferritin can be released from damaged cells in certain pathologic conditions.

    • Furthermore, certain drugs and clinical conditions such as ascorbate deficiency, fever, acute and chronic infections, and hemolysis may influence the ferritin level, producing misleading values. Despite its deficiencies, and for lack of a better practical, noninvasive test, ferritin assessment continues to be the most commonly used tool to diagnose and to monitor iron overload.

    • MRI or CT scanning is used to assess liver iron levels as a measure of total body iron load.

    • Liver biopsy may be performed to assess liver iron concentration, which is considered the most sensitive method to assess body iron burden. Again, this procedure is an invasive one and not without complications. Furthermore, because iron distribution in the thalassemic liver is uneven and could be affected by fibrosis, one can expect conflicting and inaccurate results in some patients. Grading of stainable iron or measuring parenchymal iron by atomic absorption spectroscopy has been helpful in measuring tissue iron levels, with good correlation to calculated body iron burden.

  • Cardiac complications

    • Most deaths in patients with thalassemia are due to cardiac involvement.

    • These complications range from constrictive pericarditis to heart failure and arrhythmias.

    • Transfusional hemosiderosis has been classified into 3 stages based on the number of blood units given. The higher the number of packed red blood cell (PRBC) units given, the more advanced the stage. Advanced stage is associated with more severe clinical symptoms and more abnormal findings on cardiac function studies.

    • Cardiac hemosiderosis does not occur without significant accumulation of iron in other tissues.

    • Chelation therapy has shown promising results in patients with cardiac symptoms due to iron overload.

    • Ventricular myocardium is the first site of cardiac iron deposition, while the conduction system is usually the last to be affected. The value of endomyocardial biopsy, which has been used to evaluate iron deposits in the heart, has been questioned. Iron has been reported as absent from the right ventricular subendocardium in some patients with cardiac iron overload.

    • Echocardiography, radionuclide cineangiography, and 24-hour ECG are to be used to monitor these patients.

  • Hepatic complications

    • Patients who have received regular blood transfusions for some time develop liver enlargement due to swelling of the phagocytic and parenchymal cells from the deposition of hemosiderin.

    • Liver enzyme levels are not typically elevated unless hemosiderin deposition is associated with hepatitis.

    • Chelation therapy may prevent or delay progressive liver disease, which may end in cirrhosis.

    • A report on chelation use and iron burden in North American and British thalassemia patients has shown that advances in organ-specific imaging and the availability of oral deferasirox have improved clinical care and outcome in this patient population.[29]

    • In this study,[29] 327 patients with transfusion-dependent thalassemia with age at entry (mean 22.1± 2.5 y) were followed from 2002-2011, with a mean follow up of 8 years (range 4.4-9 y). Deferasirox was the main agent used, followed by deferoxamine, and to a lesser degree, combination therapy. The use of both hepatic and cardiac MRI increased by 5-fold (P< .001) during the study period, leading to an 80% increase in the number of subjects undergoing liver iron concentration (LIC) measurements.

    • The overall results of the measurements show improvement from (median 10.7-5.1 mg/g/dry weight, but nonsignificant improvement in cardiac T2* (median 23.55-34.50 ms). The percentage of patients with markers of inadequate chelation were ferritin less than 2500 ng/mL, LIC greater than 15 mg/g/dry weight, and T2* shorter than 10 ms and also declined from 33% to 26%.[29]

    • A study by Vichinsky et al indicated that deferasirox therapy can be safe and effective long-term in young children treated for hemosiderosis. The report involved pediatric patients aged 2 years to less than 6 years, many of whom had β thalassemia, with the investigators finding that the median serum ferritin level dropped from 1702 ng/mL at baseline to 1127 ng/mL in those patients who completed 5 years of treatment.[30]

  • Long-term therapy complications

    • Because of improved medical care, patients with thalassemia are surviving their disease longer and reaching old age. With this longer survival comes new issues related to complications that need to be addressed.

    • Hepatitis C virus (HCV) has emerged as the paramount risk in patients who have been receiving blood transfusions all their lives. HCV screening was initiated in 1990. Since then, according to the Registry of the TCRN, the incidence rate of HCV has dropped significantly. The current prevalence of HCV in patients with thalassemia older than 25 years is 70%, as opposed to only 5% in those with thalassemia aged 15 years or younger.

    • Unfortunately, a high incidence rate of HCV continues in developing countries, leading to an increased incidence of fibrosis, cirrhosis, and hepatocellular carcinoma (HCC), especially in the presence of a second risk factor such as iron overload. For this reason, many centers advocate screening patients with HCV every 6 months by obtaining a fetoprotein (AFP) and an ultrasound of the liver. According to the TCRN, approximately 33% of patients with thalassemia major who are also HCV positive develop a spontaneous clearance of the HCV.

    • Two-thirds of patients with β thalassemia major have multiple calcified bilirubin stones by age 15 years.

  • Hematologic complications

    • Thrombosis was encountered in relatively significant numbers of patients with thalassemia. In a study of 83 patients with thalassemia intermedia, a 26% incidence rate of venous thromboembolic events (VTEs) was encountered, whereas only 2% of 65 patients with thalassemia major developed VTE.

    • One study determined that most of the patients with thalassemia intermedia who developed VTE had been splenectomized. Based on this fact, several centers recommend some type of prophylactic therapy to prevent thrombosis in such patients. Short-term antithrombotic therapy, both perioperatively and in the presence of thrombotic risk factors, is recommended. Patients who have undergone splenectomy and have a platelet count in excess of 600,000/µL receive low-dose daily aspirin

    • Pulmonary hypertension as a result of small pulmonary thrombi represents a significant indication of the increased risk for clotting in such patients. This complication is emerging as major cause of morbidity and mortality in patients with chronic hemolytic anemia. The incidence in such population was estimated at 10%.[31]

    • According to one study, endothelial dysfunction due to lack of bioavailability of NO is one of the main reasons for developing such complications.[32] Free plasma Hb resulting from hemolysis directly consumes NO, and the presence of arginase in the hemolysate depletes arginine, which is the substrate for NO synthetase, thus preventing generation of such product. The presence of excessive oxygen radicals in patients with chronic hemolytic anemia who are on regular packed RBC (PRBC) transfusions adds to the problem by causing rapid consumption of NO. Studies have showed that treatment with hydroxyurea may improve or prevent this complication.[19, 33]

    • Silent cerebral infarction (SCI) was diagnosed by MRI in 24% of patients with β-thalassemia/Hb E disease in a study conducted in Thailand.[34] A Cambodian child who also has β-thalassemia/Hb E disease has also been described.[35]

    • Increasing reports addressing the issue of thrombotic tendency in patients with thalassemia have revealed that such tendency is indeed seen in all types of chronic hemolytic anemia and is not limited to thalassemia intermedia as suggested earlier. Numerous factors for the thrombotic complications in this patient population were reported by many authors. A study conducted on patients with thalassemia has shown that the patients' platelets, as well as their RBCs when mixed individually with normal RBCs or normal platelets, have resulted in increased platelets adhesions; this was not noticed when control cells were used in both instances.[36] This finding may suggest that both platelets and RBCs in thalassemia could induce increased platelets adhesion which may predispose to thrombotic events.

    • Based on these reports and several others which confirm the presence of hypercoagulable state in patients with chronic hemolysis such as thalassemia and sickle cell disease, one should seriously reconsider the role of splenectomy in such conditions to avoid further risk for thrombotic events in this population of patients.[37]

  • Endocrine complications

    • People with thalassemia major frequently exhibit features of diabetes mellitus; 50% or more exhibit clinical or subclinical diabetes. This is believed to be due to defective pancreatic production of insulin, but insulin resistance also has been implicated.

    • Glucose intolerance encountered in these patients usually correlates with the numbers of transfusions received and the patient's age and genetic background.

    • A study compared the incidence of endocrinopathy in patients with thalassemia with the incidence in patients with sickle cell disease and a similar iron overload due to transfusion.[38] The study also compared patients with sickle cell disease who received transfusion with those who did not receive transfusion. The study showed that patients with thalassemia are far more prone to develop various endocrinopathies than patients with sickle cell disease. Furthermore, the incidence did not differ between patients with sickle cell disease who received transfusion and those who did not. However, the duration of transfusion was found to be a significant predictor. Thus, the underlying disease may modulate iron-related endocrine injury.

    • Osteoporosis is a severe complication of thalassemia and is thought to be related to a Wnt signaling inhibitor produced by the osteocytes, termed sclerostin, which inhibits osteoblast function. A study to evaluated circulating sclerostin in patients with thalassemia and osteoporosis who were also part of phase 2 randomized study for the effect of zoledronic acid versus placebo. Results were compared with those of healthy controls without osteoporosis and a group of women with postmenopausal osteoporosis (all patients were mostly adults). At baseline, thalassemia patients with osteoporosis had elevated circulating levels of sclerostin compared with healthy controls without osteoporosis and reduced levels of sclerostin compared with postmenopausal women with osteoporosis. Circulating sclerostin levels correlated with bone mineral density in lumbar spine, distal radius, and femoral neck. Zoledronic acid did not alter the sclerostin level after 12 months of therapy.[39]

    • In a recent publication, 26 adult women with thalassemia major were evaluated for iron-induced compromised fertility. The low gonadotropin secretion known to occur in this population to cause reduced ovarian antral follicle counts and ovarian volume was confirmed. A new player related to compromised fertility in this population was identified, however. Anti-müllerian hormone (AMH), a sensitive marker for ovarian reserve, independent of gonadotropin effect, was found to be mostly in the normal range. AMH was found to closely correlate with nontransferrin-bound iron (NTBI), indicating a role of labile iron in the pathogenesis of decreased reproductive capacity, possibly occurring in line to cardiac iron overload, which usually presents with amenorrhea and increased NTBI levels. As a result, one may conclude that AMH is an important biomarker for assessment of reproductivity in thalassemia major women, showing that fertility is preserved in the majority of women younger than 30-35 years. AMH, as wellas NTBI, are both potential markers for future studies and close monitoring to preserve fertility in this population of patients.[40]

    • Growth retardation is frequently severe in patients with thalassemia (30%). This retardation is caused, in part, by the diversion of caloric resources for erythropoiesis, as well as by the chronic anemia because hypertransfusion usually restores normal growth. Unless chelation therapy is initiated early in life, patients rarely grow normally. Excessive chelation with DFO may also cause growth retardation

    • Some clinicians recommend growth hormone testing in all children with thalassemia who are short so that those with growth hormone deficiency (GHD) can receive recombinant human growth hormone treatment. This treatment proved in this study to be effective in increasing the growth rate in all patients with thalassemia, particularly the ones with GHD.[21] The efficacy of growth hormone therapy in this population of patients was questioned in a study from Italy; the study concluded that long-term treatment with recombinant growth hormone (rGH) does not improve final height.[41]

    • The direct cause of growth retardation in these patients is thought to be an impaired growth hormone production or deficiency in production of somatomedin by the hemosiderotic liver. This has been questioned by a report that suggested GHD does not correlate with the efficacy of transfusional or chelation therapy.[42] Other factors are thought to be involved

    • Involvement of the adrenal glands or the thyroid gland may also contribute to growth failure.

  • Fertility and pregnancy complications

    • The survival of patients with thalassemia major has improved significantly. Since the introduction of effective transfusion and chelation regimens. Patients are now reaching their adulthood, and the questions regarding fertility becomes relevant. Adult patients with thalassemia major have low fertility; this was thought to be related to endocrine toxicity as a consequence to iron overload.

    • One study reported 12 patients with thalassemia major with a mean age of 24.8 years and a long history of transfusion and chelation with deferoxamine who underwent fertility evaluation tests, including semen parameters, endocrine functions, and serum zinc level.[43]

      • Fifty percent of the patients were found to have normal sperm counts, motility, and morphology; the other 6 patients had oligospermia (< 20 x 106/mL) and asthenospermia (motility < 40%).

      • Basal serum gonadotrophins (luteinizing hormone, follicle-stimulating hormone), total and free testosterone, and serum zinc levels did not differ from those found in healthy matched controls.

      • Patients with abnormal semen parameters were noticed to have low ferritin level, whereas those with high ferritin had normal sperms parameters.

      • This is an interesting observation that is not fully understood; however, it raises the question whether the abnormal sperm parameters are related to a negative effect of intensive chelation therapy.

    • Females are frequently oligomenorrheic or amenorrheic. Pregnancy complications are also seen frequently and are likely due to endocrinologic and cardiac complications. Case reports demonstrated, however, that successful pregnancy and delivery of healthy babies is possible in women with thalassemia major. Gonadal dysfunction that results in arrested or delayed puberty is reported in females with thalassemia major receiving transfusion and chelation therapy.[44] A small uterus was noted in all women with delayed or arrested puberty. The size may improve with hormonal replacement therapy (HRT).

    • Adequate transfusion to keep Hb at normal or near normal level at all times, effective chelation and early intervention with hormonal therapy may prevent permanent damage and help to preserve fertility.

  • Transfusion complications: The most common complications of blood transfusions are discussed in Treatment.

  • Chelation therapy complications: These complications and the specific adverse effects of DFO are discussed in Treatment.

  • Viral hepatitis: Viral hepatitis has been reported in nontransfused patients with iron overload, suggesting that iron overload predisposes patients to viral hepatitis, as was stated above.

Prognosis

The prognosis depends on the type and severity of thalassemia. As stated above, the clinical course of thalassemia varies greatly from mild or even asymptomatic to severe and life threatening.

Patient Education

Patients and their parents and caregivers should be made aware of the nature of their disease, the fact that it is inherited, and the need to comply with the treatments as scheduled to avoid serious complications. They should be informed that the treatment does not prevent serious complications from developing and to be aware of what to expect.

Several publications are available for patients and primary care physicians. Many support services are available, such as those offered by the Cooley Anemia Foundation, Inc., and other groups. Contact 718-321-CURE or email ncaf@aol.com.

Many of the measures used in prevention are based on educating the population and providing resources for advice and guidance. Because of the large numbers of Asian immigrants to the western United States and the high rate of thalassemia carriers among such populations, several effective programs have been initiated, especially in the state of California. Cord blood screening now includes a screen for Hb H disease in addition to the other thalassemias and hemoglobinopathies. Extensive efforts by public health and other organizations are underway to gain the trust of new immigrants and to educate them regarding the seriousness of the problem. All such measures are a first step toward more advanced educational programs for screening in order to decrease the birth rate of affected children.