Methylmalonic Acidemia (Methylmalonyl-CoA Mutase Deficiency) (MUT)



In methylmalonic acidemia (MMA), the enzyme methylmalonyl-CoA mutase (MUT) fails to break down odd-chain fatty acids and the amino acids isoleucine, valine, methionine, and threonine. A baby with MUT is either not making enough methylmalonyl-CoA mutase enzymes or is making non-working methylmalonyl-CoA mutase enzymes, or the enzymes the body is making are not working properly. A newborn screening with elevated C3, a compound that plays an essential role in metabolism, may indicate a methylmalonic acidemia condition. Signs of MUT deficiency can start at any time from birth to adulthood. In most cases, the signs begin either in the first few days or in the first few months of life.  For babies, signs of MUT deficiency can include sleeping longer or more often, tiredness, vomiting, weak muscle tone (hypotonia), fever, breathing trouble, increased number of illnesses and infections, and increased bleeding and bruising. Many of these signs may occur when a baby eats foods the body cannot break down. Symptoms can be triggered by long periods of time without eating, illnesses, and infections.

Condition Type:

Methylmalonic acidemia (MMA) is estimated to affect 1 out of every 50,000 to 100,000 babies born in the United States. Methylmalonic acidemia is caused by methylmalonyl-CoA mutase deficiency (MUT) in about half of all cases of methylmalonic acidemia.

More Information for Parents:
Also known as:
  • Methylmalonic aciduria
  • MUT
  • MCM deficiency
  • Methylmalonyl-CoA mutase deficiency
  • Methylmalonic acidemia (mutase deficiency)

Core Conditions