A probably familial saccular aneurysm of the anterior communicating artery in a neonate.

A 32-day-old boy died of recurring cerebral hemorrhages starting on the 4th day of life. Autopsy disclosed a remittingly ruptured saccular aneurysm of the anterior communicating artery. A 7-day-old brother of his had previously died of recurring subarachnoid hemorrhages as well. The young age of the patient, the site of the aneurysm, and its probably familial occurrence make this case a unique one. Nonaneurysmatic basal cerebral arteries showed remarkable histological changes partly resembling those seen in fibromuscular dysplasia, some of them probably representing preaneurysmatic alterations. A known underlying systemic disease could not be found, and immunohistochemical detection of type III collagen revealed no identifiable deficiency.