Acquired haemophilia A is a potentially severe condition characterised by spontaneous bleeding episodes. Direct recognition and prompt treatment are mandatory. Diagnostic coagulation assays show an isolated prolonged activated partial thromboplastin time, not correcting in a mixing assay. An isolated decrease of factor VIII activity together with the presence of a neutralising antibody confirm the diagnosis. Treatment consists of cessation of a possible bleed and the eradication of the neutralising antibody.