Abstract
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. Given his bone marrow biopsy result, which was positive for plasma cell myeloma, this coagulopathy was thought to be an acquired haemophilia A secondary to multiple myeloma. Anticoagulation was a challenge in this patient given his mechanical mitral valve and acquired haemophilia A. Although the patient was at risk of thrombosis due to a mechanical mitral valve, he had a bleeding diathesis and anaemia not responsive to transfusion. The decision was made to hold anticoagulation and the patient was started on myeloma treatment which included CyBorD, rituximab and daratumumab. After initiation of treatment APTT and factor VIII normalised. He eventually restarted anticoagulation under direction of his primary care doctor.