Glycogen storage disease due to lactate dehydrogenase deficiency

Glycogen storage disease due to lactate dehydrogenase (LDH) deficiency is a rare inherited metabolic disorder caused by deficiency of one of the subunits of the LDH enzyme. There are two main forms: LDH-A deficiency (also known as glycogen storage disease type XI or LDH-M subunit deficiency, caused by mutations in the LDHA gene) and LDH-B deficiency (caused by mutations in the LDHB gene). LDH is a critical enzyme in anaerobic glycolysis that catalyzes the interconversion of pyruvate and lactate. Deficiency of this enzyme primarily affects skeletal muscle and, in some cases, the skin and red blood cells. LDH-A deficiency is the more clinically significant form and typically presents with exercise intolerance, exertional myoglobinuria (dark urine after exercise due to muscle breakdown), muscle stiffness, and cramping, particularly during intense physical activity. An erythematous skin rash has also been reported in some patients. LDH-B deficiency is generally considered to be largely asymptomatic and is often discovered incidentally through routine blood tests showing low total serum LDH levels. In LDH-A deficiency, affected individuals may have elevated serum creatine kinase levels after exercise. There is currently no specific curative treatment for LDH deficiency. Management is primarily supportive and involves avoidance of strenuous exercise and other triggers that may precipitate rhabdomyolysis. Patients are counseled to moderate physical activity to prevent episodes of muscle breakdown, which in severe cases can lead to acute kidney injury. The condition has been most frequently reported in Japanese populations, though cases have been identified worldwide. Prognosis is generally favorable with appropriate lifestyle modifications.

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