[McArdle disease: report of four brothers with myophosphorylase deficiency]. / Enfermedad de McArdle: descripción de cuatro hermanos con déficit de miofosforilasa.

Myophosphorylase deficiency, or McArdle disease, is an uncommon entity. The gene for human myophosphorylase has been cloned and is located on chromosome 11, in keeping with the autosomal recessive nature of the disease and there is an excess of male patients. The diagnosis is established by documentation of elevated glycogen content and reduced phosphorylase activity in biopsied muscle tissue. We report four cases with McArdle disease which were 16, 15, 11 and 5 years old. They were brothers, and they came to the hospital because of pain, cramps and myoglobinuria after exercise or infection; in the first case, a male patient, myoglobinuria caused acute renal failure. Three of them showed reduced phosphorylase activity in biopsied muscle tissue. We discuss the different therapeutic possibilities.