Histopathology of McArdle's disease in a family

A new variant of late-onset myophosphorylase deficiency

McArdle disease classically presents in childhood or adolescence. Rarely does it become symptomatic for the first time in late adulthood, with the onset of progressive muscle wasting and weakness. Our patient is unusual in that despite a life of physical vigor, she developed immobilizing cramps, stiffness, and muscle swelling abruptly at age 60. She had no previous symptoms of muscle disease. The diagnosis was indicated by the ischemic forearm test, which produced muscle contracture and no rise in venous lactate levels, and confirmed by histochemical, electrophoretic, and biochemical studies that showed complete absence of myophosphorylase. This case defines a new variant of the late-onset type and raises important questions about compensatory mechanisms, inheritance patterns, and etiological factors in myophosphorylase deficiency.

Myophosphorylase deficiency (McArdle's disease): report of a family

The clinical and biochemical findings are presented of two brothers suffering from McArdle's Disease (Myophosphorylase Deficiency). Tissue enzyme estimations and lactate levels were done in affected and non-affected members of the family. Affected members showed absence of phosphorylase enzyme by histochemical and quantitative estimation. No quantitative abnormalities were found in other enzyme systems of glycolytic pathways in the family investigated. Various other aspects of clinical features, biochemical abnormalities and inheritance are discussed.

Myophosphorylase deficiency (McArdle's disease) in two interrelated families

The clinical and laboratory findings are presented of three patients (two affected sisters and their male cousin) with myophosphorylase deficiency in two interrelated families. Nine unaffected relatives were also investigated. Although the three patients demonstrated the characteristic features of the disease, their unaffected relatives showed no clear evidence of a heterozygous state. The genetic findings support the hypothesis that the disease is inherited as a rare autosomal recessive. A possible sex-limited mode of inheritance is discussed.