Familial occurrence of congenital aneurysm of the muscular interventricular septum.

Congenital aneurysms of the muscular interventricular septum are rare. We report two brothers with this disease and their father, who had marked thinning of part of the muscular interventricular septum with paradoxical motion. These cases lend support to the idea that these aneurysms are the result of an inherited defect in the myocardium.