A 25 year old white woman presented with a history of severe bleeding after tooth extraction for a wisdom tooth. She admitted to a long history of nose bleeds; these had occurred about once every three weeks for many years and had required blood transfusion twice. She had an appendicectomy done at the age of 11 complicated by severe bleeding that required blood transfusion. The patient said that since childhood she had easily bruised and had severe bleeding after minor cuts. She started her menarche at the age of 14 and since then had menorrhagia. She denied experiencing haematemesis, haematochezia, joint pains, shortness of breath, abdominal pain, or any other systemic complaints. The patient’s parents were healthy and she was the only child. Her only medication was oral contraceptives, which she had started about three months previously. Physical examination revealed a young woman with blond-brown hair, areas of considerable freckling on skin areas being exposed to sun, pale irides, visual acuity 20/100, and horizontal nystagmus which increased with lateral gaze. Diagnostic data included a leucocyte count of 7.6 × 10/l; packed cell volume 0.31; platelet count 178 × 10/l; prothrombin time 12.5 sec; partial thromboplastin time 23.5 sec; normal liver function tests; normal electrolytes including serum creatinine; negative urine analysis for ceroid; bleeding time 13 sec (prolonged); positive tyrosinase skin biopsy; normal pulmonary function tests; absence of dense granules in platelets evidenced by electron microscopy and aggregation defects in response to adrenaline (epinephrine), collagen, and the lowest concentration of ADP found on platelet aggregation studies (fig 1). Platelets responded normally to 2.0 × 10 m ADP.