[Muscle phosphorylase deficiency in childhood. A case report].

Myophosphorylase deficiency or McArdle's disease is rarely recognized in childhood. The onset is generally in adolescence or in adult age with exercise intolerance, muscle cramps and myoglobinuria. Two siblings of 6 and 2 years of age are described. The first patient showed early fatigue and both had elevated CK levels. Morphological and biochemical studies of muscle biopsies revealed a defect of myophosphorylase.