Pediatric Thalassemia Workup
- Author: Hassan M Yaish, MD; Chief Editor: Max J Coppes, MD, PhD, MBA more...
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. - Contrast this with the abnormalities associated with Hb H, an α thalassemia, shown below.
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 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.
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 noninvasive 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.[3] 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 was insensitive for detecting high myocardial iron. For this reason, cardiac evaluation should be addressed separately.
Hepatic iron content (HIC) obtained by liver biopsy, cardiac function tests obtained by echocardiography measurements, and multiple gated acquisition scan (MUGA) findings were compared to the results of iron measurements on R2-MRI in the liver and heart.[4] Various iron overload patients were involved in the study that 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.
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. 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).[5] 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).
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