Myelodysplastic Syndrome (MDS) is best described as?

• A. A group of preleukemic disorders causing abnormal neutrophil and platelet production
• B. Acute leukemia of B-cell origin
• C. A benign thrombocytosis
• D. A myeloproliferative neoplasm with erythrocytosis

Answer: (A)

Myelodysplastic syndromes are clonal disorders of hematopoietic stem cells that cause ineffective production and abnormal maturation of myeloid cells, leading to dysplasia in one or more blood cell lines. This results in cytopenias—anemia, and often low numbers of neutrophils and platelets—despite a cellular bone marrow. The key idea is that the problem isn’t an overproduction of mature cells, but a failure to produce properly formed cells, with abnormal development visible in the marrow.

Because these dysplastic changes reflect a premalignant clone that can evolve into acute leukemia, MDS is described as a preleukemic condition. It’s not an acute leukemia itself, which would have a high percentage of blasts and rapid progression; it’s also not a benign thrombocytosis, which implies too many platelets without dysplastic maturation, nor a myeloproliferative neoplasm with erythrocytosis, which centers on excessive red cell production.