The purposes of this study are to identify gene mutations in patients with the muscle diseases phosphofructokinase (PFK) deficiency, acid maltase deficiency (GAA deficiency) and to learn more about how these diseases develop. PFK deficiency is a mild, exercise-related illness. The childhood form of GAA deficiency (Pompe disease) affects the heart and liver and is rapidly fatal. The adult form begins in midlife and involves degeneration of skeletal muscles, leading to weakness and muscle wasting.