Frequency of attacks and severity vary. May respond to drug therapy. Muscle cramps usually occurring after exercise. Intense exercise can cause muscle destruction and possible kidney damage. In infant form, disease is generalized and severe, with heart, liver and tongue enlargement common.
Adult form involves weakness of upper arms and legs, trunk and respiratory muscles.
Muscle fatigue that, upon exercise, can lead to severe cramps, nausea, vomiting, muscle damage and discoloration of urine. Enlarged liver in infancy. Episodes of low blood sugar. Muscular symptoms may be delayed until early teens and adulthood. Generalized muscle weakness, flaccid neck muscles and inability to walk.