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."
The disease is most often 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.
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.
- Brain disease that gets worse (progressive encephalopathy)
- Developmental delays
- Failure to thrive
- Repeated yeast infections
Exams and Tests
Testing for methylmalonic acidemia is often done as part of a newborn screening exam. The United States 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:
- Ammonia test
- Blood gases
- Complete blood count
- CT scan or MRI of the brain
- Electrolyte levels
- Genetic testing
- Methylmalonic acid blood test
- Plasma amino acid test
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 health care provider 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.
Babies may not survive their first episode of symptoms from this disease.
Complications may include:
- 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 provider if your child has signs of failure-to-thrive or developmental delays.
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 provider if your child had this screening.
Kliegman RM, Stanton BF, St. Geme JW, Schor NF. Defects in metabolism of amino acids. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 85.
Madan-Khetarpal S, Arnold G. Genetic disorders and dysmorphic conditions. In: Zitelli, BJ, McIntire SC, Norwalk AJ. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 1.
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. Philadelphia, PA: Elsevier; 2013:chap 97.
Reviewed By: 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, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.