Periodic painful purpura: fact or factitious?

A 60-year-old woman with multiple psychosocial issues presented with a history of spontaneous painful bruising on her left upper arm. Extensive investigations did not reveal any abnormality apart from an elevated activated partial thromboplastin time as a result of factor XII deficiency. An autoerythrocyte sensitization test reproduced the tender bruises on her back. Our patient reported relief of pain with promethazine injections. She was subsequently referred to the psychiatric team for ongoing assessment and management. Having an awareness of this rare condition will assist in the prevention of unnecessary investigation of such cases and will allow the early referral of patients for appropriate psychological counselling.