Lactate Dehydrogenase Deficiency: Causes & Treatment
Lactate dehydrogenase deficiency is a rare inherited metabolic disorder in which the enzyme lactate dehydrogenase does not function adequately, leading to exercise intolerance and muscle pain.
Things worth knowing about "Lactate dehydrogenase deficiency"
Lactate dehydrogenase deficiency is a rare inherited metabolic disorder in which the enzyme lactate dehydrogenase does not function adequately, leading to exercise intolerance and muscle pain.
What is Lactate Dehydrogenase Deficiency?
Lactate dehydrogenase (LDH) deficiency is a very rare inherited metabolic disorder belonging to the group of glycogen storage diseases and enzymopathies. The enzyme lactate dehydrogenase (LDH) plays a central role in cellular energy metabolism, particularly in the conversion of pyruvate to lactate and back. When this enzyme is absent or impaired, the body cannot produce sufficient energy during physical exertion.
Causes
LDH deficiency is caused by mutations in the genes that encode the subunits of the LDH enzyme. The LDH enzyme consists of four subunits encoded by two different genes:
- LDHA gene (subunit A, also called the M-subunit): Mutations in this gene cause LDH-A deficiency (glycogen storage disease type XI), primarily affecting skeletal muscle.
- LDHB gene (subunit B, also called the H-subunit): Mutations in this gene cause LDH-B deficiency, mainly affecting red blood cells (erythrocytes).
Both forms are inherited in an autosomal recessive manner, meaning a child must inherit one altered gene copy from each parent to develop the condition.
Symptoms
Clinical symptoms depend on which subunit is affected:
LDH-A Deficiency (Muscle Form)
- Exercise intolerance: Symptoms appear even with moderate physical activity.
- Muscle cramps and muscle pain (myalgia) during exertion
- Myoglobinuria: Red-brown urine caused by the breakdown of muscle protein (myoglobin), indicating rhabdomyolysis.
- Elevated creatine kinase (CK) in the blood as a sign of muscle damage
- General weakness and rapid fatigue
LDH-B Deficiency (Erythrocyte Form)
- Often asymptomatic (no clinical complaints)
- Occasionally hemolytic anemia (premature breakdown of red blood cells)
- Characteristic laboratory finding: absent LDH activity in erythrocytes
Diagnosis
The diagnosis of LDH deficiency is established through several investigations:
- Blood tests: Measurement of LDH activity in serum and erythrocytes; in LDH-A deficiency, total serum LDH is reduced or undetectable.
- Exercise testing (ischemic or non-ischemic forearm test): In affected individuals, blood lactate does not rise appropriately during exercise, while ammonia rises normally -- a characteristic finding.
- Muscle biopsy: Histochemical demonstration of absent LDH activity in muscle tissue.
- Molecular genetic analysis: Identification of the causative mutation in the LDHA or LDHB gene to confirm the diagnosis.
- Urine analysis: Detection of myoglobin during acute episodes.
Treatment
There is currently no specific curative therapy for LDH deficiency. Management is symptom-oriented and includes:
- Activity modification: Avoiding intense physical exertion to prevent rhabdomyolysis episodes.
- Adequate hydration: Especially during and after physical activity, to protect the kidneys in cases of myoglobinuria.
- Emergency management of rhabdomyolysis: Inpatient treatment with intravenous fluids to prevent acute kidney injury.
- Regular medical monitoring: Surveillance of kidney function and muscle enzymes.
- Dietary measures: A carbohydrate-rich diet may help improve energy availability in some cases.
Prognosis
Life expectancy is generally not significantly reduced in most affected individuals, provided that triggers for acute episodes are consistently avoided. However, severe rhabdomyolysis episodes can lead to acute kidney injury and require prompt medical treatment. Genetic counseling is recommended for affected individuals and their families.
References
- Berardo A. et al. - A Diagnostic Algorithm for Metabolic Myopathies. In: Current Neurology and Neuroscience Reports, 2010.
- Orpha.net - Orphanet Entry: Lactate Dehydrogenase A Deficiency (ORPHA:284426), European Reference Network for Rare Diseases, 2023.
- Scriver CR. et al. (eds.) - The Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill, 8th Edition.
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