Methylmalonyl-CoA mutase deficiency

A genetic disorder affecting metabolism

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Methylmalonyl-CoA mutase deficiency is a rare metabolic disorder that affects the body's ability to process certain proteins and fats. It is a type of organic acidemia and is caused by a deficiency of the enzyme methylmalonyl-CoA mutase. This enzyme is crucial for the conversion of methylmalonyl-CoA to succinyl-CoA, a step in the breakdown of certain amino acids and fatty acids.

Pathophysiology

Methylmalonyl-CoA mutase deficiency results in the accumulation of methylmalonic acid in the blood and tissues. This accumulation can lead to metabolic acidosis, a condition where the blood becomes too acidic. The enzyme deficiency disrupts the normal metabolic pathway, leading to the buildup of toxic substances that can damage organs and tissues.

Genetics

The condition is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the defective gene, one from each parent, to be affected. The gene responsible for this condition is located on chromosome 6 and is known as the MUT gene. Mutations in this gene reduce or eliminate the activity of the methylmalonyl-CoA mutase enzyme.

Clinical Presentation

Symptoms of methylmalonyl-CoA mutase deficiency can vary widely but often include:

• Failure to thrive
• Vomiting
• Dehydration
• Developmental delay
• Seizures
• Hypotonia
• Lethargy

In severe cases, the condition can lead to coma or even death if not treated promptly.

Diagnosis

Diagnosis is typically made through a combination of clinical evaluation, biochemical testing, and genetic testing. Elevated levels of methylmalonic acid in the blood or urine are indicative of the disorder. Genetic testing can confirm mutations in the MUT gene.

Treatment

Treatment for methylmalonyl-CoA mutase deficiency often involves dietary management to limit the intake of certain proteins and fats. Patients may require a special diet low in isoleucine, valine, methionine, and threonine.

In some cases, vitamin B12 (cobalamin) supplementation may be beneficial, particularly if the deficiency is due to a defect in the cobalamin metabolism pathway. Other treatments may include medications to manage symptoms and prevent complications.

Prognosis

The prognosis for individuals with methylmalonyl-CoA mutase deficiency varies depending on the severity of the condition and the effectiveness of treatment. Early diagnosis and management can improve outcomes and quality of life.

Related pages

• Organic acidemia
• Metabolic disorder
• Autosomal recessive disorder