Inheritance of familial primary endocardial fibroelastosis

Two related families with 15 children, seven of whom developed endocardial fibroelastosis (EFE) are described. Three of the children died during infancy, and the disease was confirmed in one of them at autopsy. The survivors, two sisters age 5 years and 15 months (Family A) and two sisters age 17 and 14 years (Family B), are now symptomless and show a decrease in left ventricular hypertrophy. The mode of inheritance of EFE in our two families appears to be either autosomal or X-linked dominant with reduced penetrance.