MCC deficiency

MCC Deficiency MCC deficiency, also known as 3-Methylcrotonyl-CoA carboxylase deficiency, is a rare metabolic disorder that affects the body's ability to process certain proteins. This condition is part of a group of disorders known as organic acidemias, which are characterized by the accumulation of organic acids in the body.

Overview

MCC deficiency is caused by mutations in the MCCC1 or MCCC2 genes, which provide instructions for making the two subunits of the enzyme 3-methylcrotonyl-CoA carboxylase. This enzyme plays a critical role in the breakdown of leucine, an essential amino acid. When this enzyme is deficient or nonfunctional, leucine and its byproducts accumulate in the body, leading to a variety of health problems.

Symptoms

The symptoms of MCC deficiency can vary widely among affected individuals. Some people may remain asymptomatic, while others may experience severe symptoms. Common symptoms include:

• Developmental delay
• Hypotonia (reduced muscle tone)
• Feeding difficulties
• Vomiting
• Lethargy
• Seizures

In some cases, individuals may experience episodes of metabolic crisis, which can be life-threatening if not treated promptly.

Diagnosis

MCC deficiency is typically diagnosed through newborn screening programs that test for elevated levels of 3-hydroxyisovaleryl carnitine (C5-OH) in the blood. Confirmatory testing involves genetic testing to identify mutations in the MCCC1 or MCCC2 genes.

Treatment

There is currently no cure for MCC deficiency, but treatment focuses on managing symptoms and preventing metabolic crises. This may include:

• A low-protein diet to reduce leucine intake
• Supplementation with carnitine to help remove excess organic acids
• Regular monitoring of metabolic status

Genetics

MCC deficiency is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected. Carriers, who have one mutated gene and one normal gene, typically do not show symptoms.

Epidemiology

MCC deficiency is considered a rare disorder, with an estimated incidence of 1 in 50,000 to 1 in 100,000 live births. However, the exact prevalence may vary among different populations.

Research

Ongoing research is focused on better understanding the genetic and biochemical mechanisms of MCC deficiency, as well as developing more effective treatments. Studies are also exploring the long-term outcomes of individuals with this condition.

See Also

• Organic acidemia
• Leucine metabolism
• Newborn screening

External Links

• Genetic and Rare Diseases Information Center (GARD)
• National Organization for Rare Disorders (NORD)

NIH genetic and rare disease info

• NIH info on MCC deficiency

MCC deficiency is a rare disease.