Familial progressive bulbar and spinal muscular atrophy. Juvenile onset and late morbidity with ragged-red fibers.

Six members of a family had a neurologic disease with autosomal dominant transmission and adolescent onset of progressive wasting of predominantly distal axial muscles and muscles innervated by cranial nerves V, VII, X, and XII, leading to severe morbidity in adulthood. Muscle biopsy of the propositus revealed "ragged-red" fibers, while electromyography and autopsy material were consisted with a neurogenic disease. The case seemed unique to any clinicogenetic nosology, because it was associated with a cardiac conduction defect, a mitochondrial abnormality in skeletal muscle, and a course, distribution, and degree of weakness that included features of both chronic spinal muscular atrophy and amyotrophic lateral sclerosis.