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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 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.
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 ...
Tests that may be done to diagnose this condition include:
-
Ammonia test
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 red blood cells (RBC count)The number of white blood cells (WBC count)The tota...
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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...
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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 done on infants that looks at the amounts of amino acids in the blood. Amino acids are the building blocks fo...
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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 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
Coma
Decreased alertness is a state of reduced awareness. A coma is a state of decreased alertness from which a person cannot be awakened. A long-term co...
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- 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.
Review Date: 4/21/2015
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, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
