Acquired hemophilia A in a patient with essential thrombocythemia.

A 69-year-old woman with essential thrombocythemia (ET) developed giant ecchymosis, and she was admitted to hospital. Marked anemia (Hb 8.1 g/dl) accompanied by a prolonged activated partial thromboplastin time (89.6 s) was observed, and she received red blood cells (RBC) and fresh frozen plasma (FFP). On day 2 after admission, consciousness disturbance suddenly occurred, whereas computed tomography of the brain showed no evidence of bleeding. As the ecchymosis progressed, she developed shock. Although RBC and FFP transfusions were administered, she developed multi-organ failure and died 48 h after admission. Low factor VIII activity (<1%) accompanied by factor VIII inhibitor (17 Bethesda units) was found after her death. An autopsy revealed cerebral infarction without cerebral herniation. To date, acquired hemophilia A accompanying ET has been described in only one other patient. Although acquired factor VIII inhibitor is a rare disease, it should be tested for in ET patients with marked hemorrhagic tendency.