McArdle disease in a Druze family.

McArdle disease is reported in three generations of a consanguineous Druze family. The diagnosis was established on the basis of a failure of a rise in lactate in the ischemic forearm exercise test, glycogen accumulation in muscle fibers and the lack of myophosphorylase by histochemical and biochemical studies. The inheritance pattern is compatible with an autosomal recessive mode. Examination of family members revealed a marked variability in the clinical findings and functional status. This is the first reported case of the disorder in this ethnic group.