Thrombotic thrombocytopenic purpura associated with sickle cell-hemoglobin C disease.

Thrombotic thrombocytopenic purpura (TTP) complicated a vaso-occlusive crisis in a patient with sickle cell-hemoglobin C (HbSC) disease. Markedly abnormal HbSC red blood cell morphology confused the initial diagnostic evaluation of the peripheral smear. Sustained, severe thrombocytopenia and the patient's failure to respond clinically to RBC exchange transfusion helped to indicate the proper diagnosis that led to effective therapy.