Muscular phosphorylase deficiency in two siblings

: The clinical manifestation of McArdle disease rarely occur in children. A brother and a sister aged 12 and 7 years respectively are presented. Both are sons of a consanguinous marriage. The clinical manifestations of the girl began when she was seven. The dominant clinical feature was her difficulty in performing physical exercises. At this time the brother was asymptomatic. There were no abnormalities on physical examination. The level of the serum CK was fluctuating at a level above normal in both patients. There was not lactic acidosis after exercise test. The level of lactic acid didn't rise after McArdle test with ischemia of the forearm in both, however the plasmatic ammonium rose six or seven times above the basal level. The electromyography showed in the girl electric silence without pain and stiffness after ischemia of the forearm. The muscle biopsy performed by a Bergstrom needle showed in both a subsarcolemmal glycogen accumulations. The histochemical reaction for phosphorylase was absent, the biochemical investigations confirmed the absence of this enzyme. A hyperproteique diet did not release the clinical manifestations of the patients.