Acquired haemophilia a secondary to multiple myeloma: management of a patient with a mechanical mitral valve.

A 77-year-old man with a mechanical mitral valve on warfarin presented with an acute drop in haemoglobin and large spontaneous haematoma. He was found to have a new coagulopathy with initial labs notable for a prolonged activated partial thromboplastin time (APTT). Further workup revealed factor VIII levels less than 1%, abnormal mixing studies and elevated Bethesda titres, which was consistent with an acquired factor VIII inhibitor.