Familial skeletal myopathy with atrioventricular block

We studied familial cases of skeletal myopathy with atrial fibrillation (Af) and atrioventricular (AV) block to compare the clinical features to other myopathies associated with cardiac abnormalities.

Neurologic, cardiologic, electrophysiologic, muscle pathology, and genetic studies were performed on the patients showing muscle weakness.

Four patients (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.

Two sisters with congenital myopathy without rigid spine developed Af and AV block at the age of 28 and 18, respectively. The mother showed AV block, and underwent pacemaker implantation at the age of 63. The maternal grandmother had dilated cardiomyopathy, Af and severe lordosis. She died of stroke attacks and congestive heart failure at the age of 78. Muscle biopsy obtained from the mother and sisters showed myopathic changes without characteristic abnormalities. No mitochondrial DNA mutations were found. Other inherited myopathies with cardiac complications were not suspected in this family.

This Japanese family appears to belong to a new genetically heterogeneous group of autosomal dominant skeletal myopathy with severe AV block and Af.