Familial skeletal myopathy with atrioventricular block

Objective We studied familial eases of skeletal myopathy with atrial fibril lation (Af) and atrioventricular (AV) block to compare the clinical feature s to other myopathies associated with cardiac abnormalities. Methods Neurol ogic, cardiologic, electrophysiologic, muscle pathology, and genetic studie s were performed on the patients showing muscle weakness. Patients Four pat ients (a 63-year-old mother, 30 and 32-year-old sisters, and their maternal grandmother) and three healthy family members from three generations were studied. The mode of inheritance was suspected as autosomal dominant. Resul ts Two sisters with congenital myopathy without rigid spine developed Af an d AV block at the age of 28 and 18, respectively. The mother showed AV bloc k, and underwent pacemaker implantation at the age of 63, The maternal gran dmother had dilated cardiomyopathy, Af and severe lordosis. She died of str oke attacks and congestive heart failure at the age of 78. Muscle biopsy ob tained from the mother and sisters showed myopathic changes without charact eristic abnormalities. No mitochondrial DNA mutations were found. Other inh erited myopathies with cardiac complications were not suspected in this fam ily. Conclusion This Japanese family appears to belong to a new genetically heterogeneous group of autosomal dominant skeletal myopathy with severe AV block and Af.