Genetic defect identified in six forms (first six entries in Table 129.1). Impaired metabolism of a fuel (glycogen or lipid) necessary for muscular work (see also Chapter 85).

Exercise limited by myalgia after exertion. Myoglobinuria follows strenuous activity. Clinical diagnosis of glycogen disorders: failure of venous lactate to rise after ischemic exercise.

Phosphoglycerate kinase deficiency X-linked; others are autosomal recessive.