Coronary fibromuscular dysplasia presenting as sudden infant death.

We report an unusual case of sudden unexpected infant death in a 3-month-old boy who died of acute myocardial infarction. Histopathologic examination showed typical fibromuscular dysplasia (medial fibroplasia) in the left anterior descending coronary artery, with associated thrombus. The thoracic aorta and celiac, superior mesenteric, and renal arteries also revealed mild intimal lesions. In addition to asphyxia at delivery, a viral infection may have provoked these extensive arterial lesions. The significance of coronary arterial lesions in sudden unexpected infant death is discussed.