The effects of oral isotretinoin on the coagulation system are still not well known: some case reports describe thrombocytopenia or thrombocytosis, others present different effects on fibrinolysis. We report a case of severe acne treated with oral isotretinoin in a patient affected with haemophilia A. In this case, which differs from the only other case reported in the literature, oral isotretinoin did not appear to influence the haemophilic patient's need of factor VIII.