Cytomembranous inclusions in myelodysplastic syndrome.

A 56-year-old African-American man presented with fever of unknown origin and peripheral blood and bone marrow findings of myelodysplastic syndrome (MDS): refractory anemia with an excess of blasts in transformation that subsequently progressed to acute myeloblastic leukemia (AML). Ultrastructural study of two bone marrow specimens having the findings of MDS revealed frequent, large tubuloreticular structures (TRS) in lymphocytes, plasma cells, macrophages, and endothelial cells. Several cylindrical confronting cisternae (CCC) were present in macrophages and an endothelial cell. Two partially developed CCC were present in a plasma cell. TRS and CCC were not observed in eight subsequent bone marrow specimens obtained during the 9-month course of the AML. This is the first reported occurrence of TRS and CCC in MDS. These inclusions are probably related to an unidentified viral infection or possibly to cytokines released by the dysplastic hematopoietic cells.