Myophosphorylase deficiency: the course of an unusual congenital myopathy

A 59-year-old man had proximal weakness and wasting that started in early childhood. EMG was "myopathic," serum CK activity was increased, and muscle biopsy showed accumulations of glycogen. Biochemical studies revealed elevated glycogen concentration and absence of myophosphorylase activity. This unusual presentation of a long-standing, painless, and quite static weakness due to myophosphorylase deficiency represents another example of clinical heterogeneity.