Selective atrophy of type 1 muscle fibers in McArdle's disease.

McArdle's disease is a metabolic myopathy of glycogen utilization caused by an absence or deficiency of myophosphorylase. The muscle biopsy features include increased deposition of subsarcolemmal glycogen and absent phosphorylase histochemical staining of myofibers. We report the clinical and unique pathologic findings in three cases of McArdle's disease with prominent type 1 fiber atrophy.