• Myophosphorylase deficiency (McArdle syndrome) is an uncommon condition characterized by exercise intolerance, muscle cramping, and myoglobinuria. Although the original report by McArdle1 dealt with a sporadic case, subsequent cases reported in the literature show high familial incidence and consanguinity, implying that the defect is transmitted as a rare recessive gene or a possible sexlimited mode of inheritance. The present report describes the clinical, histoenzymatic, and biochemical findings in a 40-year-old woman with myophosphorylase deficiency. The family history reveals that four other members are also affected: an older sister, a younger brother, a 10-yearold son, and her 75-year-old mother, and possibly her maternal grandmother. Because of this particular pattern of direct transmission in this family, a dominant inheritance is postulated.
Chui LA, Munsat TL. Dominant Inheritance of McArdle Syndrome. Arch Neurol. 1976;33(9):636–641. doi:10.1001/archneur.1976.00500090042008
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