Muscle phosphoglycerate mutase deficiency: a study of a family with metabolic myopathy.

Muscle phosphoglycerate mutase deficiency results in a myopathic condition characterised by repeated cramps, possible myoglobinuria and muscle pain. We present a family with muscle phosphoglycerate mutase (PGaM) deficiency, mild glycogen storage and some exertional myalgia. Investigations of muscle biopsy tissue showed a residual PGaM activity in muscle due to a small amount of brain isoenzyme. The enzyme was also measured in blood cells and a full investigation of muscle metabolism was also carried out. Electron microscopy revealed mitochondria with similar morphological features in two patients investigated.