[Glycogenesis due to adult phosphorylase kinase deficiency]

A 42-year-old man presented exercise-induced muscle pain without myogloburia since the age of 12 years. Histochemistry and electronmicroscopy of a muscle biopsy revealed subsarcolemmal and inter-myofibrillar accumulation of glycogen. Exercise on a bicycle ergometer produced a normal raise of lactate. Biochemical study showed a partial defect in phosphorylase activity.