Segmental arterial mediolysis (SAM) is a rare arterial disorder. The cause is unknown but may be related to vasospasm or local hypoxemia.


Synonym: segmental mediolytic arteritis (SMA), segmental mediolytic arteriopathy


Clinical features:

(1) can occur at any age but more often seen in the elderly

(2) spontaneous arterial rupture with hemorrhage and shock

(3) ischemic bowel disease


Sites of lesions:

(1) superior mesenteric artery and other intra-abdominal branches of the aorta

(2) retroperitoneum

(3) coronary arteries


Angiography may show:

(1) arterial dilatation

(2) one or multiple aneurysms, which may affect several arteries or the same artery with skip lesions

(3) dissecting hematoma or dissecting aneurysm

(4) arterial narrowing, stenosis or occlusion


Pathologic features:

(1) zones of lysis within the arterial media with fibrin deposition and hemorrhage

(2) separation of the outer media from the surrounding adventitia

(3) formation of gaps in the arterial wall

(4) florid repair of the damaged arterial wall, resulting in lesions similar to fibromuscular dysplasia


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