MUSCLE PHOSPHOGLYCERATE MUTASE (PGAM) DEFICIENCY IN THE 1ST CAUCASIANPATIENT - BIOCHEMISTRY, MUSCLE CULTURE AND P-31-MR SPECTROSCOPY

Muscle phosphoglycerate mutase (PGAM) deficiency has been so far ident ified in only six patients, five of these being African Americans. We report the results of clinical, morphological, biochemical, muscle cul ture and P-31-MR spectroscopy studies in the first Caucasian patient w ith muscle PGAM deficiency. A 23-year-old man had a 10-year history of cramps after physical exertion with one episode of pigmenturia. Neuro logical examination and EMG study were normal. ECG and echocardiograph y revealed hypertrophy of the interventricular septum and slight dilat ation of the left chambers of the heart. Muscle biopsy revealed increa sed glycogen content and some accumulation of mitochondria. Muscle PGA M activity was markedly decreased (6.5% and 9.7% of control value in t wo different biopsies). Citrate synthase and other mitochondrial respi ratory chain enzyme activities were much higher than normal. In contra st to the marked decrease of PGAM activity observed in muscle biopsy, total enzyme activity in the patient's aneural muscle culture was norm al, being represented exclusively by BB isoenzyme. The deficiency of P GAM-MM isoenzyme was reproduced in the patient's innervated muscle cul ture. Muscle P-31-MR spectroscopy showed accumulation of phosphomonoes ters only on fast ''glycolytic'' exercise. On ''aerobic'' exercise, V( max), calculated from the work-energy cost transfer function, showed a n increase consistent with the morphological and biochemical evidence of mitochondrial proliferation. This might represent a sort of compens atory aerobic effort in an attempt to restore muscle power.