General Condition Information
- Cobalamin A and B deficiency
- Cobalamin A, B
- Cobalamin A,B cofactor deficiency
- Methylmalonic acidemia
- Methylmalonic acidemia (Cbl A and Cbl B forms)
- Methylmalonic acidemia (Cbl A,B)
- Methylmalonic acidemia (cobalamin conditions)
- Methylmalonic acidemia (cobalamin disorders A and B)
- Methylmalonic acidemia (cobalamin disorders, vitamin B12 disorders)
- Methylmalonic acidemia (vitamin B12 disorders)
- Methylmalonic acidemia - Cbl A B
- Methylmalonic acidemia caused by cobalamin A or cobalamin B deficiencies
- Methylmalonic acidemia CblA and CblB forms
- Methylmalonic acidemia cobalamin A, B
- Methylmalonic acidemia cobalamin disorders
- Methylmalonic acidemia due to cobalamin A,B defect
- Methylmalonic acidemia with cobalamin disorders
- Methylmalonic acidemia, cobalamin disorders
- Methylmalonic acidemia- cobalamin A,B disorders
- Methylmalonic acidemia- cobalamin defect
- Methylmalonic acidemia-Vit B 12 disorders
- Methylmalonic acidemia/vitamin B12 disorders
- Methylmalonic acidemia: Cbl A & B
- Methylmalonic acidemia: cobalamin A, B
- Methylmalonic acidemia: cobalamin disorders
- Methylmalonic acidemia: cobalamin disorders A and B
- Methylmalonyl adenosyl- cabalamine synthesis defects
- About 80 to 150 babies are born with methylmalonic acidemia each year in the United States.
- Visit GeneReviews to learn more about how often this condition occurs.
What is Methylmalonic acidemia (cobalamin disorders)
There are different forms of methylmalonic acidemia, each with different causes and treatments. Methylmalonic acidemias are inherited (genetic) conditions that prevent the body from breaking down certain proteins, cholesterol, and a type of fat called lipids.
Methylmalonic acidemias happen when an enzyme called methylmalonyl CoA mutase (mut) does not work correctly. The mut enzyme uses vitamin B-12 to help digest certain proteins, lipids, and cholesterol to use or get rid of them.
Methylmalonic acidemia (cobalamin disorders) is a type of methylmalonic acidemia that results when vitamin B-12 is not processed correctly, and so cannot help the mut enzyme work. Another type of methylmalonic academia is methylmalonic acidemia (methylmalonyl-CoA mutase).
If your baby does not have enough working mut enzyme, their body has trouble making energy and getting rid of waste. This condition can be more or less severe depending on how well this enzyme works.
If your baby’s body cannot break down proteins, fats, and cholesterol, toxins can build up. When these toxins are acids, blood can become acidic (acidemia). Acidemia can damage your baby’s body and lead to the signs and symptoms of the condition.
Newborn Screening and Follow-Up
Newborn screening for methylmalonic acidemia is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
During screening, a special machine measures how much of certain substances (called acylcarnitines) are in your baby’s blood. Your body produces these substances when it breaks down fats. Specific organic acids (called methylmalonic acid and methylcitric acid) may also be measured. Babies with high levels of these substances might have methylmalonic acidemia.
If your baby’s blood spot screening result for methylmalonic acidemia is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.
An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing. To learn more about screening results, visit the Blood Spot Screening Results page.
Your baby may need the following tests after an out-of-range screening result:
- Blood and urine tests
- Genetic testing using a blood sample
- Small skin sample
You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have very serious health problems early in life if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition can happen. Some situations can affect screening results, including:
Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.
Signs of methylmalonic acidemia can vary widely, but in most cases, health problems develop within the first few days to months of life. They can be triggered by eating foods that the body cannot break down or by going long periods without eating. Illness or infection can also trigger symptoms. Milder forms of methylmalonic acidemia may not appear until later in infancy or childhood.
Signs of the condition may include the following:
Methylmalonic acidemia (Cbl A.B) is caused by changes in either the MMAA or MMAB gene. The MMAA and MMAB genes give your body instructions for proteins that are needed to process vitamin B-12, which helps the enzyme methylmalonyl CoA mutase (mut) to work.
Without a working MMAA or MMAB gene, your baby's body cannot make enough of the proteins needed for methylmalonyl CoA mutase to work well. As a result, their body has trouble breaking down proteins, lipids, and cholesterol. Their body cannot make enough energy, and harmful toxins build up and damage their body.
- Methylmalonic acidemia is an autosomal recessive condition. Babies inherit the condition when each parent passes down the same nonworking gene that causes methylmalonic acidemia (MMAA or MMAB) to their baby. Only babies with two matching nonworking genes—for example, one nonworking MMAA from the mom and one nonworking MMAA from the dad—have this condition. Babies with two nonworking genes that do not match—for example, one nonworking MMAA from the mom and one nonworking MMAB from the dad—will not have this condition.
- People with one working copy and one nonworking copy of the MMAA or MMAB gene are called carriers.
- Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
- If two parents are carriers of a nonworking copy of the MMAA or MMAB gene, they have a 1 in 4 chance of having a child with methylmalonic acidemia.
- Carriers for methylmalonic acidemia often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with methylmalonic acidemia.
- Parents who already have a child with methylmalonic acidemia still have a 1 in 4 chance of having another child with methylmalonic acidemia. This 1 in 4 chance stays the same for all future children.
- Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.
Treatment and Management
It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.
Treatments may include the following:
- Diet low in certain proteins and fats
- Special formulas and foods for children with methylmalonic acidemia
- Regular and frequent meals and snacks
- Vitamin B-12 supplements (only for certain types of methylmalonic acidemia), usually given by a shot (injection) rather than by mouth
- Carnitine supplements in some cases
Children who receive early intervention and treatment for methylmalonic acidemia can have healthy growth and development. Even with treatment, some children may still have developmental delays or learning difficulties.