Genetics and aneurysm formation.

This article reviews the current understanding of genetic factors involved in the development of intracranial aneurysms. Of the large number of heritable connective tissue disorders that have been associated with intracranial aneurysms, three are discussed in detail: autosomal dominant polycystic kidney disease, Ehlers-Danlos syndrome type IV, and alpha 1-antitrypsin deficiency. The author reviews the familial occurrence of intracranial aneurysms, which is found in about one-fifth of patients with aneurysm subarachnoid hemorrhage. Guidelines are provided for the evaluation of patients with familial intracranial aneurysms and screening of their relatives.