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Epidemiology and Etiology
- Myelodysplastic syndromes (MDSs) comprise a heterogeneous group of myeoid neoplasms that are broadly characterized by cytopenias associated with a dysmorphic and usually cellular bone marrow and an increased risk of leukemic transformation. The median age at diagnosis is ≥65 years for de novo MDS. Cytopenias in MDS are due to clonal abnormalities of marrow cells affecting one or more cell lines, ultimately leading to reduced hematopoiesis. Therapy-related myeloid neoplasms, including acute myeloid leukemia (AML) and MDS, account for 10%–20% of all myeloid neoplasms.
- Environmental factors such as exposure to chemicals, radiation, and chemotherapy, as well as genetic syndromes and benign hematologic disorders (such as paroxysmal nocturnal hemoglobinuria), have been associated with an increased risk of MDS.
- Chromosome abnormalities occur in up to 80% of cases, leading to accumulation of multiple genetic lesions, loss of tumor suppressor genes, and/or activating oncogene mutations.