Myelodysplastic syndrome with complex chromosome abnormalities and peculiar fibril formation in granulocytes

We report a case of myelodysplastic syndrome with peculiar fibril formation in granulocytes shown through electron microscope and complex karyotypic abnormalities including ring chromosomes. The patient, a 76-year-old male, was consulted for mild pancytopenia in February 1987. After 5 month, his hematological findings showed severe pancytopenia getting worse rapidly and presence of blasts in the peripheral blood. He had slightly hypercellular marrow with marked trilineage dysplasia and increased number of blasts (12.6%). Chromosome analysis from the bone marrow cells revealed its various structural abnormalities, especially in No. 3, 4, 5, 7, 11 with translocation on 11q11, and large ring chromosomes derived from unknown one. By electron microscopic study, we observed bizarre structures, which was peculiar fibril formation as bundles of filament resembling actin paracrystals, throughout cytoplasm as well as within nucleus in granulocytes.