Muscle phosphoglycerate mutase (PGAM) deficiency: a second case.

Muscle phosphoglycerate mutase (PGAM) activity was markedly decreased (6% of the normal mean) in a 17-year-old girl with recurrent myoglobinuria after intense exercise. Muscle biopsy showed increased PAS stain; glycogen concentration was twice normal. Studies of anaerobic glycolysis in vitro showed decreased lactate production with glycogen, and with all hexose phosphate glycolytic intermediates, which was corrected by addition of purified PGAM to the reaction mixtures. A defect of the M subunit of PGAM was documented by electrophoretic, heat lability, and mercury inhibition studies. Intermediate PGAM activities (39 and 50% of normal) were found in muscle biopsies from the patient's asymptomatic parents. These data confirm the clinical, morphologic, and biochemical features described in the first patient with PGAM deficiency and suggest autosomal-recessive transmission of the trait.