This report describes two patients, a father and son, with autosomal dominant Emery-Dreifuss muscular dystrophy. Although the father had the common phenotype, the son had a severe phenotype including early onset of weakness and fatal cardiomyopathy in childhood. Among the patients with severe phenotype of autosomal dominant Emery-Dreifuss muscular dystrophy, he is the first to have familial onset, and in the severe end of this disease spectrum.