Balloon-like platelets in myelodysplastic syndromes--a feature of dysmegakaryopoiesis?

Large bizarre platelets are a frequent finding in the peripheral blood of the myelodysplastic syndrome (MDS). In this study we describe a distinct subpopulation of platelets in MDS which by phase contrast microscopic examination seems to have a balloon-shaped bulge of the cell membrane. Increased numbers of these atypical platelets were found in 24 of 27 MDS patients (89%). Only 3 patients, all with ringsideroblastic anemia, had normal platelet morphology. The number of atypical platelets were negatively correlated (r = 0.44; p = 0.021) to the peripheral platelet counts in MDS. Among 48 patients with acute leukemia, chronic lymphoproliferative or chronic myeloproliferative disorders, 13 (27%) had atypical platelets. Here, but not in the MDS group, atypical platelets seemed to be associated with recent chemotherapy. In a group of patients with benign hematological disorders abnormal platelet morphology was seen only occasionally. The described atypical platelets most likely reflect maturation disturbances of the megakaryopoiesis. An increased value (greater than 1%) in a cytopenic patient would suggest a diagnosis of MDS, unless associated with recent cytotoxic therapy.