Development of acquired haemophilia A in a patient treated with alemtuzumab for multiple sclerosis.

This case illustrates a 36-year-old man who presented with a factor VIII (FVIII) inhibitor (acquired haemophilia A) with cutaneous bleeding and a significant thigh haematoma. No traditional risk factors for the development of a FVIII inhibitor were identified. However, previous treatment with alemtuzumab for multiple sclerosis was noted in the patient's history. Alemtuzumab is an anti-CD52 monoclonal antibody and is known to be associated with the development of a number of autoimmune conditions, with a delay in onset of these conditions as long as 5 years after the cessation of treatment. To our knowledge, there have only been three previously documented cases of a FVIII inhibitor in the setting of alemtuzumab therapy. This case adds further evidence to the current body of literature suggesting alemtuzumab as a causative agent for the development of an FVIII inhibitor.