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For further information, see CMDT Part 13-28: Myelodysplastic Syndromes

Key Features

Essentials of Diagnosis

  • Cytopenias with hypercellular bone marrow

  • Morphologic abnormalities in one or more hematopoietic cell lines

General Considerations

  • Group of acquired clonal disorders of the hematopoietic stem cell, characterized by the constellation of cytopenias, a usually hypercellular marrow, morphologic dysplasia and genetic abnormalities

  • Causes

    • Idiopathic (most common)

    • Prior exposure to cytotoxic chemotherapy or radiation therapy

  • In addition to cytogenetics, sequencing can detect genetic mutations in 80–90% of patients

  • Acquired clonal mutations identical to those seen in myelodysplastic syndrome can occur in the hematopoietic cells of ∼10% of apparently healthy older individuals, defining the disorder of clonal hematopoiesis of indeterminate potential (CHIP)

  • Myelodysplasia encompasses several heterogeneous syndromes; a key distinction is whether there is an increase in bone marrow blasts (> 5% of marrow elements)

    • MDS with excess blasts represents a more aggressive form of the disease, often leading to acute myeloid leukemia

    • Patients without excess blasts are characterized by the degree of dysplasia, eg, MDS with single lineage dysplasia and MDS with multilineage dysplasia

    • The morphologic finding of ringed sideroblasts is used to define a subcategory of the lower risk MDS syndromes

    • Patients with isolated 5q loss, which is characterized by the cytogenetic finding of loss of part of the long arm of chromosome 5, comprise an important subgroup of patients with a different natural history

    • Chronic myelomonocytic leukemia (CMML): a proliferative syndrome, including sustained peripheral blood monocytosis > 1000/mcL

Demographics

  • Occurs most often in patients aged > 60

Clinical Findings

Symptoms and Signs

  • Asymptomatic, with incidentally found cytopenias

  • Fatigue, infection, or bleeding is related to bone marrow failure

  • Wasting, fever, weight loss

  • Splenomegaly

  • Pallor

  • Bleeding

  • Signs of infection

  • Paraneoplastic syndromes of various sorts (prior to or following diagnosis)

Differential Diagnosis

  • AML (≤ 20% blasts)

  • Aplastic anemia

  • Anemia of chronic disease

  • Vitamin B12 or folate deficiency

  • Megaloblastic anemia

  • Myelofibrosis

  • HIV-associated cytopenias

  • Acute or chronic drug effect

Diagnosis

Laboratory Tests

  • Anemia may be marked

  • Mean cell volume is normal or increased

  • Peripheral blood smear may show macro-ovalocytes

  • White blood cell count usually normal or reduced; neutropenia is common

  • Neutrophils may exhibit morphologic abnormalities, including deficient numbers of granules, or bilobed nucleus (Pelger-Huet abnormality)

  • Myeloid series may be left shifted with small numbers of promyelocytes or blasts

  • Platelet count is normal or reduced; hypogranular platelets may be present

Diagnostic Procedures

  • Bone marrow aspirate and biopsy are characteristically hypercellular but may occasionally be hypocellular

  • Signs of abnormal erythropoiesis include

    • Megaloblastic features

    • Nuclear budding

    • Multinucleated erythroid precursors

  • Prussian blue stain may demonstrate ringed sideroblasts

  • Myeloid series is often left shifted with variable increases in blasts

  • Deficient or abnormal myeloid granules ...

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