Portal Hypertension in Myeloid Metaplasia

Introduction The spleen in myeloid metaplasia is the principal site of extramedullary blood formation. In the past, progressive splenomegaly has been thought to reflect an attempt to compensate for a hypofunctioning bone marrow.1Myeloid metaplasia is now thought by many investigators to be a chronic myeloproliferative disorder,2,3akin to chronic myelocytic leukemia, polycythemia vera, megakaryocytic leukemia, and erythroleukemia. In myeloid metaplasia, there is proliferation of primitive mesenchymal cells and their derived cell types, as well as the fibroblasts and osteoblasts. The interrelationships within this group of disorders are illustrated by patients with polycythemia vera, who, after a variable period, develop myeloid metaplasia with striking leukoerythroblastic changes in the peripheral blood, anemia, marked splenomegaly, and progressive marrow fibrosis. This picture is indistinguishable from that of patients with "primary" myeloid metaplasia and osteomyelosclerosis and myelofibrosis. Evidence suggesting portal hypertension has been occasionally reported in patients with myeloid metaplasia.4-6Hickling