Acute multi-organ failure syndrome is a rare and life-threatening complication of patients with sickle cell disease. The syndrome appears to be reversed with prompt, aggressive exchange transfusion therapy. It has been attributed to widespread vascular occlusion due to micro-vascular red cell sickling. We present a case of severe multi-organ failure in a patient with sickle thalassemia and mild clinical course, who had clinical and laboratory features consistent with thrombotic thrombocytopenic purpura (TTP). The dramatic response to therapy with plasma exchange, a treatment often effective in TTP, suggests a similarity in pathophysiology of micro-vascular occlusion and multi-organ failure in sickle cell disease.