Red cell aplasia in myelofibrosis with myeloid metaplasia. A distinct functional and clinical entity.

Three patients with myelofibrosis with myeloid metaplasia are described. All three presented with grave anemia and red cell aplasia. Erythroid failure was the functional characteristic of erythropoiesis as resulted from erythrokinetic studies. Bone marrow was hypercellular or normocellular with hyperplasia of granuloblasts and megakaryocytes. Despite absent or mild splenomegaly at diagnosis, massive splenomegaly associated with a leukoerythroblastic blood film developed during the course of the disease. A relative young age (42-47 years), a subacute course of the disease and terminal blast crisis in two of them were the prominent clinical features of the patients. The differentiation from acute or malignant myelofibrosis is discussed. The patients appear to be a distinct subset within myelofibrosis with myeloid metaplasia