Clinico-hematologic Features of Myelodysplastic Syndrome Presenting as Isolated Thrombocytopenia: An Entity with a Relatively Favorable Prognosis

The existence of isolated cytopenia in myelodysplastic syndrome (MDS) has been described, however, the exact clinico-hematologic features of such MDS patients are still obscure. The aim of this study was to provide additive clinico-hematologic information on MDS patients with isolated thrombocytopenia in comparison with idiopathic thrombocytopenic purpura (ITP). We searched for MDS with isolated thrombocytopenia in 146 sequential patients with MDS and evaluated their clinical features at the time of MDS diagnosis. We found 13/146 (8.9%) patients with MDS showing isolated thrombocytopenia. These patients were male predominant (10:3) and were all diagnosed as refractory anemia after reassessment of marrow findings, however, two of them had an initial diagnosis of ITP. Leukemic transformation was rarely noted (1/13 patients), but 1 patient developed myelofibrosis. Cytogenetic study demonstrated that 3 patients had del(20q), 2 had t(1;7)(q10;p10), and 5 showed normal karyotypes. The most prominent morphologic feature in the megakaryocytes was the presence of micromegakaryocytes (5/13) and 8/13 had hypogranulated neutrophils, whereas pseudo-Pelger nuclear anomaly was rarely detectable. Of note is that 7/13 patients had an increased number of megakaryocytes in the marrow. Most patients survived for more than 2 years. Approximately 9% of MDS patients showed isolated thrombocytopenia and most of them had a favorable prognosis. Some MDS patients with isolated thrombocytopenia have been mistakenly diagnosed as having ITP, since approximately 50% of our MDS patients with isolated thrombocytopenia had an increased number of megakaryocytes with low grade dysplasia. Therefore, careful attention to differential diagnosis is recommended for these patients.