Methylmalonic acidemia
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 most often diagnosed in the first year of life. It is an autosomal recessive disorder. This 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
- Seizures
- Vomiting
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.
Newborn screening exam
Newborn screening tests look for developmental, genetic, and metabolic disorders in the newborn baby. This allows steps to be taken before symptoms ...
Read Article Now Book Mark ArticleTests that may be done to diagnose this condition include:
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Blood ammonia test
Blood ammonia test
The ammonia test measures the level of ammonia in a blood sample.
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Blood gases
Blood gases
Blood gases are a measurement of how much oxygen and carbon dioxide are in your blood. They also determine the acidity (pH) of your blood.
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Complete blood count
Complete blood count
A complete blood count (CBC) test measures the following:The number of white blood cells (WBC count)The number of red blood cells (RBC count)The numb...
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CT scan or MRI of the brain
CT scan
A computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body. Related tests include:Abdomin...
Read Article Now Book Mark ArticleMRI of the brain
A head MRI (magnetic resonance imaging) is an imaging test that uses powerful magnets and radio waves to create pictures of the brain and surrounding...
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Electrolyte levels
Electrolyte levels
A comprehensive metabolic panel is a group of blood tests. They provide an overall picture of your body's chemical balance and metabolism. Metaboli...
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Methylmalonic acid blood test
Methylmalonic acid blood test
The methylmalonic acid blood test measures the amount of methylmalonic acid in the blood.
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Plasma amino acid test
Plasma amino acid test
Plasma amino acids is a screening test, usually done on infants that looks at the amounts of amino acids in the blood. Amino acids are the building ...
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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 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.
Outlook (Prognosis)
Babies may not survive their first episode of symptoms from this disease. Those who survive often have problems with the development of the nervous system, although normal cognitive development can occur.
Possible Complications
Complications may include:
-
Coma
Coma
Decreased alertness is a state of reduced awareness and is often a serious condition. A coma is the most severe state of decreased alertness from whi...
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- Kidney failure
- Pancreatitis
- Cardiomyopathy
- Recurrent infections
- Hypoglycemia
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
- Developmental delays
Prevention
A low-protein diet can help reduce the number of 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.
References
Gallagher RC, Enns GM, Cowan TM, Mendelsohn B, Packman S. Aminoacidemias and organic acidemias. In: Swaiman KF, Ashwal S, Ferriero DM, et al, eds. Swaiman's Pediatric Neurology. 6th ed. Elsevier; 2017:chap 37.
Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM. Defects in metabolism of amino acids. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 103.
Madan-Khetarpal S, Arnold G, Ortiz D. Genetic disorders and dysmorphic conditions. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 1.
Review Date: 4/28/2023
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.