A case report of siblings with hypertrophic cardiomyopathy that progressed to dilated cardiomyopathy--case reports.

The authors encountered 2 brothers with hypertrophic cardiomyopathy (HCM), both of whom were later found to have progressed to dilated cardiomyopathy (DCM). Case No. 1 (younger brother): A diagnosis of HCM without left ventricular (LV) dilatation was made at age two by cardiac catheterization and echocardiogram. However, he had been well until age thirteen when dyspnea developed. Echocardiograms showed LV wall thickening (septum 20 mm, and posterior 18 mm) and LV dilatation (left ventricular diastolic diameter [LVDd] 60 mm) accompanied by LV dysfunction (ejection fraction [EF] 18%). At autopsy, the heart weighed 875 g and showed LV dilatation with thickened walls. Case No. 2 (elder brother): At age twelve, he was found to have an increased heart size on x-ray when his family was evaluated owing to his brother's condition. Cardiac catheterization and echocardiogram showed HCM without LV dilatation. He remained asymptomatic until age twenty when dyspnea developed, at which echocardiography showed a dilated LV. The authors speculate that the HCM with progression to DCM is an atypical type of familial HCM and that progression to DCM is genetically determined.