MEDizzy - A 65-year-old man presents with increasing fatigue and

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Hematology

A 65-year-old man presents with increasing fatigue and shortness of breath. Examination of his peripheral blood finds pancytopenia, and a few (less than 5%) immature cells are present. Some of the neutrophils are bilobed (Pelger-Huët change) and a dimorphic red blood cell population is seen. A bone marrow biopsy reveals a hypercellular marrow with about 15% of the cells being immature cells. Approximately 20% of the red cell precursors have iron deposits that encircled the nucleus. Which of the following is the most likely cause of these clinical findings?

ExplanationThe myelodysplastic syndromes (MDS) are a group of disorders characterized by defective hematopoietic maturation and an increased risk of developing acute leukemia. These disorders characteristically have hypercellular bone marrows but pancytopenia in the peripheral blood. The two basic types of MDS are an idiopathic (primary) form and a therapy-related (secondary) form. Both have numerous dysplastic features affecting all blood cell lines. Red cell dysplastic features include the presence of ringed sideroblasts, megaloblastoid erythroid precursors, and misshapen erythroid precursors. A dimorphic population of red cells may be seen in the peripheral blood of some patients with some types of MDS. White cell dysplastic features include hypogranular cells or Pelger-HuÎt white blood cells, which are abnormal appearing neutrophils having only two nuclear lobes. Megakaryocytes may be abnormal and have only a single nuclear lobe or multiple separate nuclei, so-called “pawn ball” megakaryocytes. Chromosomal abnormalities are commonly associated with the MDSs, especially 5q and trisomy 8.