McArdle's disease: case report and review of the literature.

McArdle's disease, or myophosphorylase deficiency, is one of the most common muscle glycogenoses and typically presents in childhood or adolescence with exercise intolerance, myalgia, myoglobinuria, and cramps in the exercising muscle. We report the case of a 21-year-old male patient with liver enzyme elevation who had a history of weakness, exercise intolerance, and muscle cramps since childhood. His sister (a three-year- old) suffered from similar symptoms. Laboratory results showed that serum creatinine phosphokinase levels were elevated serum lactate did not rise on ischemic exercise testing, while muscle biopsy showed subsarcolemmal and intermyofibrillar periodic acid schiff-positive vacuoles filled with glycogen. This case report underlines the importance of taking into account rare metabolic diseases such as muscle glycogenoses in the evaluation of patients with elevated liver enzymes.