Massive ascites caused by peritoneal extramedullary hematopoiesis as the initial manifestation of myelofibrosis

An 83-year-old man presented with massive ascites, Cytological examination of the ascites revealed primitive hematopoietic cells. The specimen of bone marrow biopsy disclosed diffuse fibrosis, which suggested myelofibrosis wi th extramedullary hematopoiesis as the cause of ascites. His symptoms resol ved dramatically after administration of hydroxyurea. Ascites formation in myelofibrosis is often attributed to presinusoidal portal hypertension and occurs in the context of well-established disease. This case demonstrates t hat myelofibrosis may manifest as massive ascites caused by peritoneal impl ants of myeloid tissues. Extramedullary hematopoiesis should be included in the differential diagnosis of ascites.