Spontaneous haemothorax caused by costal exostosis.

We report a case of spontaneous haemothorax in a 19 year old boy with an exostosis of the left second rib. It may have been caused by nontraumatic rupture of markedly dilated pleural vessels, as a result of long-standing friction between the exostosis and the pleura. This is the first report of spontaneous haemothorax, without penetrative injury to the pleura or the diaphragm, in a patient with hereditary multiple exostosis.