McArdle’s syndrome

TypeV Myophosphorylase deficiency, McArdle s syndrome Absence of muscle phosphorylase Diminished exercise tolerance muscles have abnormally high glycogen content (2.5-4.1%). Little or no lactate in blood after exercise. 

Glycogen phosphorylase deficiency in muscle gives rise to muscle weakness, frequent cramp and ease of fatigue (McArdle s syndrome). It also gives rise to hypoglycae-mia if the liver enzyme is deficient (Chapter 6). 

Phenylketonuria Alcaptonuria Hyperammonemia I Hyperammonemia II McArdle s syndrome Hypophosphatasia Congenital lactase deficiency Hereditary fructose intolerance Gout... 

Type V (McArdle s syndrome) May be elevated during episodes of severe rhab-domyolysis (G25)... 

Ross BD, Radda GK, Gadian DG, Rocker G, Esiri M and Ealconer-Smith J (1981) Examination of a case of suspected McArdle s syndrome by nuclear magnetic resonance. New England Journal of Medicine 304 1338-1342. 

Leloir s discovery of UDP-glucose at about the same time provided the answer. Persons with McArdle syndrome are greatly benefit-ted by a high-protein diet, presumably because amino acids such as alanine and glutamine are converted efficiently to glucose and because branched-chain amino acids may serve as a direct source of muscle energy.c,d... 

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