Systemic malignancies as a cause of unexpected microangiopathic hemolytic anemia and thrombocytopenia.

Tumor cells from malignancies of any type-carcinoma, sarcoma, lymphoma, leukemia-may cause systemic arteriolar and capillary obstructions. The high shear rates of blood passing through these obstructions result in fragmentation of the red cells and can cause severe anemia, described as microangiopathic hemolytic anemia (MAHA).The thrombi caused by these obstructions consume platelets and can lead to severe thrombocytopenia. MAHA (defined by fragmented red cells on the peripheral blood smear and evidence of hemolysis) and thrombocytopenia are the clinical features of syndromes described as thrombotic microangiopathies (TMAs). If a malignancy is not recognized as the cause of TMA, the diagnosis of thrombotic thrombocytopenic purpura (TTP) may be considered and plasma exchange, the essential treatment for TTP, may be initiated-a critical decision because this treatment carries a high risk of serious complications. This review describes the clinical features that should suggest a search for systemic malignancy as the cause of unexpected MAHA and thrombocytopenia. Recognition of a systemic malignancy is critical to the initiation of appropriate chemotherapy and avoidance of inappropriate use of plasma exchange treatment.