Myelofibrosis with myeloid metaplasia is classified broadly as a chronic myeloid disorder and, more specifically, as a chronic myeloproliferative disease¹ (Figure 1). The primary pathogenetic mechanism is a clonal stem-cell disorder that leads to ineffective erythropoiesis, dysplastic-megakaryocyte hyperplasia, and an increase in the ratio of immature granulocytes to total granulocytes. This clonal myeloproliferation is characteristically accompanied by reactive myelofibrosis (bone marrow fibrosis) and by extramedullary hematopoiesis in the spleen or in multiple organs. The diagnosis is often suspected when teardrop-shaped red cells and myeloid precursors are detected in the peripheral blood. The typical clinical features include marked splenomegaly, progressive anemia, . . .