Methylmalonic acidemia

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Definition

Methylmalonic acidemia is a disorder in which the body cannot break down certain proteins and fats. The result is a buildup of a substance called methylmalonic acid in the blood. This condition is passed down through families.

It is one of several conditions called an "inborn error of metabolism."

Causes

The disease is usually diagnosed in the first year of life. It is an autosomal recessive disorder, which means the defective gene must be passed onto the child from both parents.

A newborn with this rare condition may die before it is ever diagnosed. Methylmalonic acidemia affects boys and girls equally.

Symptoms

Babies may appear normal at birth, but develop symptoms once they start eating more protein, which can cause the condition to get worse. The disease can cause seizures and stroke.

Symptoms include:

  • Brain disease that gets worse (progressive encephalopathy)
  • Dehydration
  • Developmental delays
  • Failure to thrive
  • Lethargy
  • Repeated yeast infections
  • Seizures
  • Vomiting

Exams and Tests

Testing for methylmalonic acidemia is often done as part of a newborn screening exam. The US Department of Health and Human Services recommends screening for this condition at birth because early detection and treatment is helpful.

Tests that may be done to diagnose this condition include:

Treatment

Treatment consists of cobalamin and carnitine supplements and a low-protein diet. The child's diet must be carefully controlled.

If supplements do not help, the doctor may also recommend a diet that avoids substances called isoleucine, threonine, methionine, and valine.

Liver or kidney transplantation (or both) have been shown to help some patients. These transplants provide the body with new cells that help breakdown methylmalonic acid normally.

Outlook (Prognosis)

Babies may not survive their first episode of symptoms from this disease.

Possible Complications

  • Coma
  • Death
  • Kidney failure

When to Contact a Medical Professional

Seek medical help right away if your child is having a seizure for the first time.

See a pediatrician if your child has signs of failure-to-thrive or developmental delays.

Prevention

A low-protein diet can help reduce the number of acidemia attacks. People with this condition should avoid those who are sick with contagious illnesses, such as colds and the flu.

Genetic counseling may be helpful for couples with a family history of this disorder who wish to have a baby.

Sometimes, expanded newborn screening is done at birth, including screening for methylmalonic acidemia. You can ask your health care provider if your child had this screening.

References

Rezvani I, Rosenblatt DS. Valine, leucine, isoleucine, and related organic acidemias. In: Kliegman, RM, Behrman RE, St. Geme III JW, Schor NF, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 79.

Vockley J. Organic acidemias and disorders of fatty acid oxidation. In: Rimoin D, Korf B, eds. Emery and Rimoin's Principles and Practice of Medical Genetics. 6th ed. Elsevier Ltd; 2013:chap 97.

Version Info

  • Last reviewed on 4/21/2015
  • Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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