Vitamin B12 responsive methylmalonicaciduria

Vitamin B12 responsive methylmalonicaciduria is a rare metabolic disorder characterized by the body's inability to properly process certain fats and proteins, leading to a buildup of methylmalonic acid in the blood. This condition is one of the types of methylmalonic acidemia, which can lead to various health issues if not treated. The term "responsive" indicates that the disorder can be managed or improved with Vitamin B12 supplementation.

Causes

Vitamin B12 responsive methylmalonicaciduria is caused by mutations in specific genes that are involved in the metabolism of certain amino acids, fatty acids, and cholesterol. These mutations lead to a deficiency in the activity of the enzyme methylmalonyl-CoA mutase, which requires Vitamin B12 (cobalamin) as a cofactor. The deficiency in this enzyme's activity results in the accumulation of methylmalonic acid in the body.

Symptoms

Symptoms of Vitamin B12 responsive methylmalonicaciduria can vary widely among affected individuals but may include:

• Vomiting
• Lethargy
• Failure to thrive
• Developmental delay
• Muscle weakness
• Hypotonia (decreased muscle tone)
• Anemia
• Ketosis
• Hyperammonemia (elevated levels of ammonia in the blood)

Diagnosis

Diagnosis of Vitamin B12 responsive methylmalonicaciduria typically involves a combination of clinical evaluation, laboratory testing, and genetic testing. Laboratory tests may include blood tests to measure levels of methylmalonic acid, ammonia, and other substances, as well as urine tests to detect abnormal organic acids. Genetic testing can identify mutations in the genes associated with the disorder.

Treatment

Treatment for Vitamin B12 responsive methylmalonicaciduria primarily involves supplementation with Vitamin B12 to reduce the levels of methylmalonic acid in the blood. The amount and frequency of supplementation can vary depending on the severity of the condition and the individual's response to treatment. Dietary management, including a low-protein diet, may also be recommended to reduce the intake of the amino acids that are metabolized to methylmalonic acid. In some cases, additional treatments such as liver transplantation may be considered.

Prognosis

The prognosis for individuals with Vitamin B12 responsive methylmalonicaciduria can vary. Early diagnosis and treatment can improve the outcome and may help prevent or minimize complications. However, even with treatment, some individuals may experience ongoing health issues, including developmental delays and chronic kidney disease.

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