A 26-year-old Indian woman with known hemoglobin E disease presented with epistaxis and petechial hemorrhage. Her hemoglobin concentration, usually around 96 g/l, was 88 g/l and her reticulocyte count was 3.8%. Because of alarm at a platelet count of < 10 × 109/l, she was immediately given 3 units of platelets before doing any further investigations. Early the next morning she became disoriented with increasing confusion and subsequently lost consciousness. Magnetic resonance imaging revealed occlusion of a cerebral vessel with microthrombi. A peripheral blood film showed predominantly target cells and irregularly contracted cells, reflecting her hemoglobin E disease, but there were also some spherocytes and small numbers of red cell fragments (image). Severe thrombocytopenia was confirmed. The serum lactate dehydrogenase (LDH) was 840 iu/l (normal range: 200–450) with a mild increase in urea and creatinine. Coagulation tests were normal. A diagnosis of thrombotic thrombocytopenic purpura (TTP) was suspected and was confirmed by showing marked reduction of plasma ADAMTS13 (<5%, normal range: 40–130%).
The patient was treated by plasma exchange with fresh frozen plasma, plus rituximab. Her serum LDH level returned to normal within a few days. The platelet count rose to 40 × 109/l by day 2 and subsequently stabilized at 100–120 × 109/l.
The examination of a blood film is of crucial importance in any unexplained thrombocytopenia, both to confirm that a low platelet count is not factitious and to seek evidence of the cause of the thrombocytopenia, particularly TTP or other microangiopathic thrombopathy. Platelet transfusion can aggravate TTP and is therefore contraindicated. Early diagnosis and treatment is crucial as the mortality of untreated cases is as high as 90%. Patients should be treated without waiting for the classic pentad to develop.