Refractory thrombocytopenia. A myelodysplastic syndrome that may mimic immune thrombocytopenic purpura.

The French-American-British classification scheme of myelodysplastic syndromes includes a category of refractory cytopenia that includes refractory thrombocytopenia (RTC). Because dysmegakaryopoiesis manifesting as an isolated cytopenia can be difficult to identify morphologically and because it may be accompanied by megakaryocytic hyperplasia, RTC may be confused with idiopathic thrombocytopenic purpura. A review of 1,220 cases of myelodysplastic syndromes at Mayo Clinic Jacksonville and Mayo Clinic Rochester from 1979 to 1990 yielded 9 cases (0.7%) of isolated thrombocytopenia (RTC) associated with clonal chromosome abnormalities. Review of 319 marrow chromosome analyses performed at the cytogenetics laboratory at Mayo Clinic Rochester from 1979 to 1990 for patients with low platelet count yielded two additional cases of RTC (0.6%). Of the 11 RTC cases, 3 previously had been misdiagnosed as idiopathic thrombocytopenic purpura. All patients had oval macrocytes in peripheral blood smears and abnormal megakaryocyte morphology in bone marrow aspirates, lacked antiplatelet antibodies, and did not have splenomegaly on clinical examination. The most common clonal chromosome abnormalities involved chromosomes 3, 5, 8, or 20. Steroid therapy was ineffective. Clinical and laboratory findings can establish the diagnosis of RTC and allow the physician to avoid recommending inappropriate therapy (steroids or splenectomy) for these patients.