Cystic adventitial disease (CAD) is a rare cause of intermittent claudication, occurring in approximately 1:1200 claudicants or 1:1000 of those undergoing arteriography. It is most often described in the popliteal artery and is characterised by a mucinous cyst located in the adventitia of the artery, the contents of which resemble those of a ganglion. The origins of adventitial cysts are unknown, but connections to adjacent synovial spaces have been identified, suggesting that the cyst is a variant of a ganglion. In this report, we discuss a rare case of severe mucoid degeneration of the intima and media in a 67-year-old Saudi male patient. The patient presented with a saccular aneurysm of his right "mid-arm" brachial artery and critical ischemia of his right hand from distal embolisation.