One-year follow-up in a child with McArdle disease: exercise is medicine.

A 9-year-old boy with McArdle disease, who demonstrated remarkable recovery of objectively measured exercise tolerance after 1 year of follow-up, during which he pursued age-appropriate physical activities. The patient presented 1 year previously with severe myalgia, muscle weakness, proteinuria, hematuria, hyperthermia, and elevated creatine kinase levels after noncompetitive swimming. At that time, he reported a 3-year history of general myalgia and poor exercise tolerance. He was diagnosed with McArdle disease by both biochemical and genetic methods. Subsequently he performed a maximal exercise test and was prescribed a return to age-appropriate physical activity (protected by a pre-exercise dietary consumption of approximately 20 g carbohydrate). At 1-year follow up, he reported no subsequent acute clinical episodes, no general problems with exercise either at school or in ordinary activities, a virtual normalization of serum creatine kinase levels, and a 14% increase in body mass-adjusted peak oxygen uptake (from 18.8 to 21.8 mL O2/kg/min). The results suggest that, with protection by increasing pre-exercise blood glucose with carbohydrate ingestion, a substantially normal lifestyle may be possible in some children with McArdle disease.