The bone marrow has three myeloid cell lines: granulocytic, erythroid, and megakaryocytic. The MDS may affect one or more myeloid cell lines, resulting in anemia, neutropenia, and/or thrombocytopenia.
MDS causes normocytic or macrocytic (non-megaloblastic) anemia. The hemoglobin is typically less than 10 g/dL. The reticulocyte count is normal to low, and patients are usually transfusion-dependent. The anemia in MDS is refractory to any replacement therapy (iron, B12, or folate).
Neutropenia (decreased neutrophil count) and thrombocytopenia (reduced platelet count) are also observed in MDS. Patients with MDS commonly have neutrophil counts less than 1,800/µL and platelet counts less than 100,000/µL.
Organomegaly (large liver and spleen) is not commonly observed in MDS, unlike myeloproliferative neoplasm (chronic myelogenous leukemia), associated with liver and spleen enlargement.
Patients are not diagnosed with MDS without complete knowledge of clinical and drug history. Repeated bone marrow biopsies over several months may be necessary in some cases to establish this diagnosis.
