Glycogen storage disease due to lactate dehydrogenase M-subunit deficiency

A rare glycogen storage disease characterized by easy fatigue, exertional myalgia, painful muscle stiffness, and cramps, with or without myoglobinuria. Pustular psoriasis-like eruptions with antecedent annular scaly plaques may be observed in some patients. In affected women, pregnancy may be complicated by abdominal pain and dystocia.