Hematologic aspects of systemic mastocytosis.

Systemic mast cell disease is characterized by bone marrow involvement by mast cells and frequently by peripheral blood cytopenias. The coexistence of hematologic disorders, such as myeloproliferative or myelodysplastic syndromes, or of lymphoreticular malignancies with SMCD is common. Overt mast cell leukemia is rare. In general, patients who coexhibit a severe hematologic disorder tend to have a more compressed clinical course and a worse prognosis. Hemorrhage can be a result of heparin release from stimulated mast cells.