What is Methylmalonic Acidemia, MMUT-related?

Methylmalonic acidemia represents a group of disorders that affect the way a person breaks down proteins and fats. Methylmalonic acidemia, MMUT-related is caused by harmful genetic changes (mutations) in the MMUT gene (formerly known as the MUT gene). In general, methylmalonic acidemia may manifest any time between the neonatal period and adulthood. The most common presentation is a severe onset during infancy, referred to as the "mut0" subtype. Some individuals may present with less severe or later-onset presentations, referred to as the "mut–" subtype. Symptoms often develop as an episode due to infection or other external stressors (metabolic decompensation) and may include vomiting, dehydration, excessive tiredness (lethargy), and seizures. Long-term complications can include increased risk for infections, low muscle tone (hypotonia), brain damage (encephalopathy), developmental delay, intellectual disability, poor growth (failure to thrive), pancreatitis, enlarged liver (hepatomegaly), and chronic kidney disease that progresses to kidney failure.

How common is Methylmalonic Acidemia, MMUT-related?

The incidence of methylmalonic acidemia is estimated to be between 1 in 50,000 and 1 in 100,000 live births, but the exact incidence is unknown. Five genes are known to cause methylmalonic acidemia with approximately 60% of cases being attributed to mutations in MMUT.

How is Methylmalonic Acidemia, MMUT-related treated?

There is no cure for methylmalonic acidemia. Treatment involves managing acute crises (metabolic decompensation) and long-term management. Metabolic crises are managed in a hospital and involve increasing the amount of fluid in the body, ensuring proper nutrition (reduced or no protein and increased glucose-intake), and monitoring the patient for signs of further complications. Long-term management mainly includes a high-calorie diet that is low in protein. Additional treatments may include vitamin B12 intramuscular injections, carnitine and other supplements, and antibiotics. Transplant may become necessary if organ failure occurs.

What is the prognosis for an individual with Methylmalonic Acidemia, MMUT-related?

Methylmalonic acidemia is associated with several chronic issues and higher-than-average mortality rates. Even with treatment, patients may develop intellectual disability or kidney failure. Metabolic crisis can lead to coma, especially if left untreated. For patients with early presentations, there is a significant risk of death within the first few years of life.

Other names for
methylmalonic acidemia, MMUT-related

  • Isolated methylmalonic acidemia
  • MMA
  • Methylmalonic aciduria


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