Laboratory Studies
CBC (differential and peripheral blood smear)
Peripheral blood count reveals anemia, neutropenia, and/or thrombocytopenia. The anemia is often macrocytic. Cytopenias can evolve and progress over a period of weeks to months.
The blood smear commonly reveals macrocytosis, hypogranular granulocytes, pseudo–Pelger-Huet anomaly (hypogranular and hypolobulated granulocytes), and giant platelets. Reticulocyte counts are low despite normal numbers of erythroid progenitors in the marrow. In JMML, marked monocytosis may be present.
Bone marrow aspirate and trephine core biopsy
See Procedures and Histologic Findings.
Quantitative hemoglobin electrophoresis
This may reveal elevated hemoglobin F levels, indicating reversion to fetal erythropoiesis due to bone marrow stress.
Cytogenetic studies (conventional karyotype, fluorescence in situ hybridization (FISH), polymerase chain reaction)
These studies reveal chromosomal abnormalities in 40-70% of pediatric cases of myelodysplasia syndrome (MDS).
Acquired chromosome abnormalities confirm the diagnosis when myelodysplasia syndrome is suspected.
The most commonly known abnormalities include monosomy 7 or 7q, monosomy 5 or 5q, or trisomy 8. myelodysplasia syndrome may also be associated with 20q, isochromosome 17, and abnormalities of 11q. Reciprocal translocations and inversions are uncommon.
Children who present with a peripheral blood and/or bone marrow disorder associated with t(8;21)(q22;q22), inv(16)(p13.1q22) or t(16;16)(p13.1;q22) or t(15;17)(q22;q12) should be considered to have AML regardless of the blast count. [4]
Fanconi anemia test
A Fanconi screen using diepoxybutane (DEB) or mitomycin C stimulation reveals abnormal chromosome breakage if this syndrome is present.
Paroxysmal nocturnal hemoglobinuria (PNH) test
Measurement of 2 complement regulatory proteins, CD55 (decay accelerating factor [DAF]) and CD59 (membrane inhibitor of reactive lysis [MIRL]) aids in diagnosis of PNH. The clinical picture of PNH is rare in childhood, although PNH clones in the absence of hemolysis or thrombosis may be observed in children with refractory cytopenia of childhood (RCC).
Human leukocyte antigen (HLA) typing
Human leukocyte antigen (HLA) typing of patient and family members should be performed at the outset, in anticipation of allogeneic hematopoietic stem cell transplantation (HSCT).
Additional laboratory studies
In most cases, myelodysplasia syndrome is diagnosed after a history and physical examination, followed by the laboratory workup described above. In some instances, additional tests may be warranted.
Viral serologies, especially human immunodeficiency virus (HIV), cytomegalovirus (CMV), EBV, and parvovirus, can be used to exclude viral etiologies of altered hematopoiesis.
The novo or primary form of myelodysplasia syndrome in children should be distinguished from cases of secondary myelodysplasia syndrome that follow congenital or acquired bone marrow failure syndromes [27] and from therapy-related myelodysplasia syndrome that follows cytotoxic therapy for a previous neoplastic or nonneoplastic condition.
Imaging Studies
Imaging studies do not contribute to establishing the diagnosis or prognosis of myelodysplasia syndrome.
Procedures
Bone marrow aspiration and biopsy are essential to establish the diagnosis and to classify the myelodysplasia syndrome.
Biopsy findings are needed to ascertain cellular architecture, cellularity, percentage of blasts, and the presence of fibrosis.
Bone marrow findings are reviewed under Histologic Findings.
As myelodysplasia has a varied temporal course, these procedures may need to be repeated at different time points if initial studies are not confirmatory and there is no alternate explanation for clinical/laboratory findings.
Histologic Findings
Bone marrow aspiration and biopsy are essential diagnostic tools. [28] The minimal morphologic criteria for the diagnosis of myelodysplasia syndrome remains similar in the most recent WHO classification system: In the appropriate clinical setting, at least 10% of the cells of at least 1 myeloid bone marrow lineage (erythroid, granulocytic, megaryocytic) must show unequivocal dysplasia for the lineage to be considered dysplastic. [4] Bone marrow biopsy should also be performed to assess cellularity and architecture because fibrosis can be a component of disease. The bone marrow of patients with myelodysplasia syndrome can be normocellular or hypocellular. [29] Hypocellularity of the bone marrow is more commonly observed in childhood myelodysplasia syndrome than in older patients.
Because the diagnosis of myelodysplasia syndrome relies heavily on marrow morphology, interobserver and intraobserver differences complicate disease classification. The FAB system, defined by a consensus of hematologists and hematopathologists, should be used in characterizing marrow results. The current FAB system is strictly based on morphology and does not take into account cytogenetics or predisposing abnormalities, which limits its use in children. [30] The changing classification schemes and continuing controversies underscore the fact that the understanding of myelodysplasia is evolving. [31, 32, 33]
As noted previously, the WHO classification system published in 2008 devotes a section to childhood myelodysplasia syndrome; a provisional entity, refractory cytopenia of childhood (RCC) is introduced in the classification for the first time. The category of RCC is reserved for childhood cases with less than 2% blasts in peripheral blood and less than 5% blasts in the bone marrow and persistent cytopenias associated with dysplasia in at least 2 cell lineages. [4, 34]
The morphological findings of RCC are illustrated in the following table. [4]
Children with myelodysplasia syndrome and 2-19% blasts in peripheral blood and/or 5-19% blasts in the bone marrow are categorized using the same criteria as adults with myelodysplasia syndrome. [34] In contrast to adults, isolated refractory anemia is uncommon in children with myelodysplasia syndrome, who more commonly present with thrombocytopenia and/or neutropenia, often accompanied by a hypocellular bone marrow. [32]
The WHO classification includes some cytogenetic information; the most recently proposed WHO classification scheme for myelodysplasia syndrome is as follows: [4]
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Refractory cytopenia with unilineage dysplasia - Refractory anemia, refractory neutropenia, refractory thrombocytopenia
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Refractory anemia with ringed sideroblasts
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Refractory anemia with multiple dysplasia
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Refractory anemia with excess blasts
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Myelodysplastic syndrome with isolated del(5q)
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Myelodysplastic syndrome, unclassifiable
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Childhood myelodysplastic syndrome - Provisional entity: Refractory cytopenia of childhood (RCC)
JMML is unique to the pediatric age group and hence categorized separately from myelodysplasia syndrome. This disease is characterized by the absence of t(9;22), an absolute peripheral monocyte count of higher than 450/mcL, elevated hemoglobin F levels, selective in vitro hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF), and excessive proliferation of monocyte-macrophage colonies in clonogenic culture. In JMML, nearly 75% of patients demonstrate mutually exclusive mutations of PTPN11, NRAS or KRAS, or NF1, all of which encode signaling proteins in RAS-dependent pathways.
Diagnostic Challenges
Diagnostic problems arise when the clinical or laboratory findings suggest myelodysplasia syndrome but the morphologic findings are inconclusive; when secondary dysplasia is caused by nutritional deficiencies, medications, toxins, growth factor therapy, inflammation, or infection or when bone marrow hypocellularity or myelofibrosis obscures the underlying disease process. [35]
Per the most recent WHO classification system, if myelodysplasia syndrome has inconclusive morphologic features, a presumptive diagnosis of myelodysplasia syndrome can be made if a specific clonal abnormality is present. However, the list [4] is not fully inclusive (not included, but significant if found: del(20), trisomy 8 and –Y). These abnormalities, reported in some adult patients with aplastic anemia or other cytopenias are associated with favorable response to immunosuppressive therapy. [36] This emphasizes the variation in temporal evolution of the disease and should be kept in mind for clinical decision making.
Hypocellular myelodysplasia syndrome may be more common in children because of the relative prevalence of inherited marrow failure syndromes. Hence, if no MDS-related cytogenetic abnormalities are present, the distinction between childhood MDS and evolving aplastic anemia or congenital bone marrow failure syndrome can be very difficult. Therefore, at least 2 biopsies obtained at least 2 weeks apart are recommended to facilitate the detection of representative bone marrow spaces containing foci of erythropoiesis. [4]
The morphological changes in the bone marrow of children with hypoplastic RCC are compared with those with aplastic anemia in table 2. [4]
Morphological findings of hypoplastic refractory cytopenia of childhood and aplastic anemia of childhood.
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Morphological findings of refractory cytopenia of childhood.
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Morphological findings of hypoplastic refractory cytopenia of childhood and aplastic anemia of childhood.
