3-Methylcrotonyl-CoA carboxylase deficiency

A rare metabolic disorder affecting leucine metabolism

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3-Methylcrotonyl-CoA carboxylase deficiency (3-MCC deficiency) is a rare metabolic disorder that affects the body's ability to break down certain proteins, specifically the amino acid leucine. This condition is part of a group of disorders known as organic acidemias.

Pathophysiology

3-Methylcrotonyl-CoA carboxylase deficiency is caused by a deficiency of the enzyme 3-methylcrotonyl-CoA carboxylase (3-MCC), which is necessary for the metabolism of leucine. This enzyme deficiency leads to the accumulation of toxic substances in the body, which can cause a variety of health problems.

Genetics

The disorder 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 associated with this condition is located on chromosome 3.

Symptoms

Symptoms of 3-MCC deficiency can vary widely among affected individuals. Some may remain asymptomatic, while others may experience:

• Hypotonia
• Developmental delay
• Seizures
• Vomiting
• Lethargy
• Hypoglycemia

Diagnosis

Diagnosis of 3-MCC deficiency is typically made through newborn screening programs, which detect elevated levels of 3-hydroxyisovaleryl-carnitine in the blood. Further confirmatory tests include urine organic acid analysis and genetic testing.

Treatment

Management of 3-MCC deficiency involves dietary modifications to limit leucine intake and prevent metabolic crises. In some cases, supplementation with carnitine may be beneficial. Regular monitoring by a metabolic specialist is recommended.

Prognosis

The prognosis for individuals with 3-MCC deficiency varies. Many individuals with the condition lead normal lives with appropriate management, while others may experience significant health challenges.

Related pages

• Organic acidemia
• Leucine
• Metabolic disorder
• Newborn screening

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  Methylcrotonyl-CoA

3-Methylcrotonyl-CoA carboxylase deficiency

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