A rare cause of thoracic outlet syndrome.

First rib pathology can narrow the thoracic outlet thus producing compression of the brachial plexus and subclavian vessels. There have been only three case reports of neurogenic thoracic outlet syndrome (TOS) caused by a nonunion of the first rib and there have been no reports of a first rib malunion causing TOS. A rare case of TOS caused by a malunion of the first rib is presented.