Acquired myopathy/dystrophies.

Diseases of muscle may be congenital or acquired. They cause muscle weakness without sensory loss. The onset, distribution, and clinical course help to differentiate the type of muscle disorder. The diagnostic workup may include laboratory examination, electrodiagnostic studies, and muscle biopsy. A definitive diagnosis leads to better decision making with regard to treatment, genetic education, prognosis, functional expectations, and the impact of exercise on muscle function.