Lactate dehydrogenase deficiency type B

Lactate Dehydrogenase Deficiency Type B is a rare metabolic disorder characterized by a deficiency in one of the forms of lactate dehydrogenase (LDH), specifically the LDH-B isoform. This enzyme plays a crucial role in the glycolysis pathway, facilitating the conversion of pyruvate to lactate under anaerobic conditions. The deficiency leads to a variety of symptoms and complications, primarily affecting muscular and cardiac tissues.

Symptoms and Diagnosis

Patients with Lactate Dehydrogenase Deficiency Type B may exhibit a range of symptoms, often triggered by physical activity or infections. These symptoms include muscle cramps, fatigue, and exercise intolerance. Unlike other metabolic disorders affecting the glycolysis pathway, this condition does not typically lead to myoglobinuria (presence of myoglobin in urine) following intense physical activity.

Diagnosis of this condition involves biochemical assays to measure LDH activity in the blood, with a specific focus on the LDH-B isoform. Genetic testing can confirm mutations in the LDHB gene, which provides instructions for making the B subunit of the lactate dehydrogenase enzyme.

Genetics

Lactate Dehydrogenase Deficiency Type B is inherited in an autosomal recessive pattern. This means that to be affected, an individual must have a copy of the mutated gene from both parents. The condition is caused by mutations in the LDHB gene, located on chromosome 12p12. The LDHB gene mutations result in reduced or absent activity of the LDH-B enzyme, disrupting the normal process of lactate production and utilization.

Treatment and Management

There is no specific cure for Lactate Dehydrogenase Deficiency Type B. Treatment focuses on managing symptoms and preventing complications. Avoiding strenuous exercise and adopting a diet low in simple carbohydrates may help manage exercise intolerance and reduce symptoms. In some cases, supplementation with coenzyme Q10 has been suggested to improve muscle function, although evidence is limited.

Epidemiology

Lactate Dehydrogenase Deficiency Type B is an extremely rare condition, with only a handful of cases reported in the medical literature. Due to its rarity, the exact prevalence is unknown.

See Also

• Metabolic disorder
• Glycolysis
• Lactate dehydrogenase
• Pyruvate
• Myoglobinuria

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