The authors describe the case of a middle-aged women who presented with an acute myocardial infarction due to thrombotic occlusion of angiographically normal coronary arteries. Coronary thrombosis was caused by a hypercoagulable state related to a haemolytic crisis of paroxysmal nocturnal haemoglobinuria and the patient was treated conservatively with antithrombotic agents. The clinical course was complicated by both severe bleeding and thrombotic complications and the patient eventually died of a massive intracerebral haemorrhage. The rapid occurrence of complications inhibited a timely administration of a specific treatment for complement-mediated haemolysis (eculizumab).