Abstract
We record a case of pulmonary arteriovenous fistula presenting in a dramatic and unusual way. These lesions are generally diagnosed clinically by consideration of their associated features. In this case these were all absent, and the patient presented with a spontaneous haemothorax as an isolated finding. When blood is found on aspiration of the pleural cavity it generally represents bloodstained effusion (trauma excluded), and by far the commonest cause is bronchogenic carcinoma. Less frequently, however, aspiration of blood may represent spontaneous intrapleural bleeding without effusion (spontaneous haemothorax), and a rare cause of this situation is pulmonary arteriovenous fistula. We record this case to demonstrate that innocent pulmonary arteriovenous fistulae can masquerade as carcinoma.