Genetic Fact Sheets for Parents

Fatty Acid Oxidation Disorders

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Disorder Name: Carnitine palmitoyl transferase deficiency, type 2
Acronym: CPT-2 deficiency

This fact sheet contains general information about CPT-2 deficiency. Every child is different and some of this information may not apply to your child specifically. Not all is known about CPT-2 deficiency and, at present, there is no standard treatment plan. Certain treatments may be recommended for some children but not others. Children with CPT-2 deficiency should be followed by a metabolic doctor in addition to their primary doctor.

What is CPT-2 deficiency?

CPT-2 deficiency stands for “carnitine palmitoyl transferase deficiency – type 2”. It is one type of fatty acid oxidation disorder. People with CPT-2 deficiency have problems breaking down fat into energy for the body. 

Fatty Acid Oxidation Disorders:

Fatty acid oxidation disorders (FAODs) are a group of rare inherited conditions. They are caused by enzymes that do not work properly.

A number of enzymes are needed to break down fats in the body (a process called fatty acid oxidation). Problems with any of these enzymes can cause a fatty acid oxidation disorder. People with FAODs cannot properly break down fat from either the food they eat or from fat stored in their bodies.

The symptoms and treatment vary between different FAODs. They can also vary from person to person with the same FAOD. See the fact sheets for each specific FAOD.

FAODs are inherited in an autosomal recessive manner and affect both males and females.

What causes CPT-2 deficiency?

CPT-2 deficiency occurs when an enzyme, called “carnitine palmitoyl transferase – type 2” (CPT-2), is either missing or not working properly. This enzyme’s job is to help change certain fats in the food we eat into energy. It also helps us use fat already stored in the body.

CPT-2 Diagram

Energy from fat keeps us going whenever our bodies run low of their main source of energy, a type of sugar called glucose. Our bodies rely on fat when we don’t eat for a stretch of time – like when we miss a meal or when we sleep. 

When the normal enzyme is missing or not working, the body cannot use fat for energy, and must rely solely on glucose. Although glucose is a good source of energy, there is a limited amount available. Once the glucose has been used up, the body tries to use fat without success. This leads to low blood sugar, called hypoglycemia, and to the build up of harmful substances in the blood.

If CPT-2 deficiency is not treated, what problems occur?

A small number of babies with CPT-2 deficiency show symptoms shortly after birth. Others don’t start showing the effects until later in infancy. Most people do not have symptoms until their teen years or early adulthood. This is called the “classic” form of CPT-2 deficiency. 

Babies and children who show early signs of CPT-2 deficiency have episodes of illness called metabolic crisis. Some of the first signs of a metabolic crisis are:

Other symptoms then follow:

If a metabolic crisis is not treated, a child with CPT-2 deficiency can develop:

CPT-2 deficiency in newborns
Rarely, a baby with CPT-deficiency shows symptoms in the newborn period.  Newborns with symptoms usually have many episodes of metabolic crisis. Other health effects in newborns can be:

  Some babies are also born with:

Without treatment, babies who have symptoms in the newborn period usually die very early in life. 

CPT-2 deficiency in infants and children
A small number of children with CPT-2 deficiency start showing symptoms in late infancy or early childhood. If untreated, some of the effects can be:

Without treatment, many children with CPT-2 deficiency die early in life.  

Symptoms of metabolic crisis in babies and children with CPT-2 deficiency often happen after having nothing to eat for more than a few hours. Symptoms are also more likely when a baby or child with CPT-2 deficiency gets sick or has an infection.

Some children with CPT-2 deficiency have never had a metabolic crisis or other related health problems and are only found to be affected after a brother or sister has been diagnosed. 

CPT-2 deficiency in adults
Most people with CPT-2 deficiency have the adult form. This is also called “classic” CPT-2 deficiency, or the “muscle” form. 

Symptoms of classic CPT-2 deficiency usually start between 15 and 30 years of age. Periods of muscle weakness are common. Breakdown of muscle fibers can happen. Symptoms usually happen during heavy exercise or after going without food for a long period of time. Signs of muscle breakdown include:

Adults who are not treated can develop kidney failure. 

Classic CPT-2 deficiency does not cause metabolic crises or heart problems. 

What is the treatment for CPT-2 deficiency?

Your baby's primary doctor will work with a metabolic doctor to care for your child. Your doctor may also suggest that you meet with a dietician familiar with CPT-2 deficiency.

Certain treatments may be advised for some children but not others. When necessary, treatment is usually needed throughout life. The following are treatments sometimes recommended for babies and children with CPT-2 deficiency:

1.  Avoid going a long time without food 
Infants and young children with CPT-2 deficiency need to eat frequently to prevent a metabolic crisis. Your metabolic doctor will tell you how often your child needs to be fed.  In general, it is often suggested that infants be fed every four to six hours. Some babies need to eat even more frequently than this. It is important that infants be fed during the night. They may need to be woken up to eat if they do not wake up on their own. Your metabolic doctor and dietician will give you an appropriate feeding plan for your infant. Your doctor will also give you a ‘sick day’ plan tailored to your child’s needs for you to follow during illnesses or other times when your child will not eat.

Your metabolic doctor will continue to advise you on how often your child should eat as he or she gets older.  When they are well, many teens and adults with CPT-2 deficiency can go without food for up to 12 hours without problems. The other treatments usually need to be continued throughout life. 

2.  Diet
Sometimes a low fat, high carbohydrate food plan is recommended. Carbohydrates give the body many types of sugar that can be used as energy. In fact, for children needing this treatment, most food in the diet should be carbohydrates (bread, pasta, fruit, vegetables, etc.) and protein (lean meat and low-fat dairy foods). Any diet changes should be made under the guidance of an experienced dietician.

Children with CPT-2 deficiency cannot use certain building blocks of fat called "long chain fatty acids".  Your dietician can help create a food plan low in these fats. Much of the rest of the fat in the diet will likely be in the form of medium chain fatty acids.

Ask your doctor whether your child needs to have any changes in his or her diet.

3.  MCT oil and L-carnitine
Medium Chain Triglyceride oil (MCT oil) is often used as part of the food plan for people with CPT-2 deficiency. This special oil has medium chain fatty acids that can be used in small amounts for energy. Your metabolic doctor or dietician can guide you in how to use this supplement.

Some children and adults may be helped by taking L-carnitine. This is a safe and natural substance that helps body cells make energy. It also helps the body get rid of harmful wastes. Your doctor will decide whether or not your child needs L-carnitine. Unless you are advised otherwise, use only L-carnitine prescribed by your doctor.  Do not use any supplements without checking with your doctor.   

4. Call your doctor at the start of any illness
Always call your health care provider right away when your child has any of the following:

Babies and children with CPT-2 deficiency need to eat extra starchy food and drink more fluids during any illness - even if they may not feel hungry – or they could have a metabolic crisis. Children who are sick often don’t want to eat. If they won’t or can’t eat, they may need to be treated in the hospital to prevent a metabolic crisis.  Ask your metabolic doctor if you should carry a special travel letter with medical instructions for your child’s care.

5.  Avoid long periods of exercise and avoid getting cold 
Long periods of strenuous exercise can trigger symptoms in both children and adults. So can cold weather. Muscle effects can include:

If muscle symptoms occur, prompt treatment is needed to prevent kidney damage. Children or adults with muscle symptoms should:

To help prevent muscle symptoms:

What happens when CPT-2 deficiency is treated?

Treatment can help prevent or control symptoms in some children with CPT-2 deficiency. Children who are treated early may be able to live healthy lives with typical growth and development. Some children do continue to have episodes of metabolic crisis and other health problems despite treatment.

When treated, adults with the classic form of CPT-2 deficiency are expected to live healthy lives.

What causes the CPT-2 enzyme to be absent or not working correctly?

Genes tell the body to make various enzymes. People with CPT-2 deficiency have a pair of genes that do not work correctly. Because of the changes in this pair of genes, the CPT-2 enzyme either does not work properly or is not made at all. 

How is CPT-2 deficiency inherited?

CPT-2 deficiency is inherited in an autosomal recessive manner. It affects both boys and girls equally. 

Everyone has a pair of genes that make the CPT-2 enzyme. In children with CPT-2 deficiency, neither of these genes works correctly. These children inherit one non-working gene for the condition from each parent. 

Parents of children with CPT-2 deficiency are rarely affected with the disorder. Instead, each parent has a single recessive gene for CPT-2 deficiency. They are called carriers for CPT-2 deficiency. Carriers do not have CPT-2 deficiency because the other gene of this pair is working correctly. In most cases, carriers of CPT-2 deficiency do not have any symptoms of the disease. However in a small number of cases, carriers of CPT-2 have been reported with symptoms of the disorder.

When both parents are carriers, there is a 25% chance in each pregnancy for the child to have CPT-2 deficiency. There is a 50% chance for the child to be a carrier, just like the parents. And, there is a 25% chance for the child to inherit two working genes. 

Autosomal Recessive Inheritance Chart

Genetic counseling is available to families who have children with CPT-2 deficiency. Genetic counselors can answer your questions about how CPT-2 deficiency is inherited, choices during future pregnancies, and how to test other family members. Ask your doctor about a referral to a genetic counselor.

Is there genetic testing available?

Genetic testing for CPT-2 deficiency can be done on a blood sample. Genetic testing, also called DNA testing, looks for changes in the pair of genes that cause CPT-2 deficiency. In some children, both gene changes can be found. However, in other children, neither or only one of the two gene changes can be found, even though we know they are present.

DNA testing is not necessary to diagnose your child. It can be helpful for carrier testing or prenatal diagnosis, discussed below.

What other testing is available?

CPT-2 deficiency can also be confirmed by an enzyme test on a skin sample. Talk to your doctor or your genetic counselor if you have questions about testing for CPT-2 deficiency. 

Can you test during pregnancy?

If both gene changes have been found in your child with CPT-2 deficiency, DNA testing can be done during future pregnancies. The sample needed for this test is obtained by either CVS or amniocentesis.

If DNA testing would not be helpful, an enzyme test can be done on cells from the fetus. Again, the sample needed for this test is obtained by either CVS or amniocentesis.     

Parents may either choose to have testing during pregnancy or wait until birth to have the baby tested. A genetic counselor can talk with you about your choices and answer questions about prenatal testing or testing your baby after birth. 

Can other members of the family have CPT-2 deficiency or be carriers?

Having CPT-2 deficiency
The brothers and sisters of a baby with CPT-2 deficiency have a chance of being affected, even if they haven’t had symptoms. Finding out whether other children in the family have CPT-2 deficiency is important because early treatment may prevent serious health problems. Talk with your doctor or genetic counselor about testing your other children for CPT-2 deficiency.

CPT-2 deficiency carriers
Brothers and sisters who do not have CPT-2 deficiency still have a chance to be carriers like their parents. Except in special cases, carrier testing should only be done in people over 18 years of age. 

Each of the parents’ brothers and sisters has a 50% chance to be a CPT-2 deficiency carrier. It is important for other family members to be told that they could be carriers. There is a very small chance they are also at risk to have children with CPT-2 deficiency. Most commonly, carriers of CPT-2 deficiency do not have any symptoms of the disease. However a small number of carriers of CPT-2 have been reported to have symptoms of the disorder.

Some states do not offer newborn screening for CPT-2 deficiency. However, expanded newborn screening through private labs is available for babies born in states that do not screen for this condition. To learn more about expanded newborn screening, see How to obtain MS/MS.

When both parents are carriers, newborn screening results are not sufficient to rule out CPT-2 deficiency in a newborn baby. In this case, special diagnostic testing should be done in addition to newborn screening.

During pregnancy, women carrying fetuses with CPT-2 deficiency may be at increased risk to develop serious medical problems. Some women carrying fetuses with Fatty Acid Oxidation Disorders have developed:

All women with a family history of CPT-2 deficiency should share this information with their obstetricians and other health care providers before and during any future pregnancies. Knowing about these risks allows better medical care and early treatment if needed. 

Can other family members be tested?

Diagnostic Testing
Brothers and sisters of an affected child can be tested for CPT-2 deficiency using either a DNA test or a special enzyme test. 

Carrier Testing
If both gene changes have been found in the child with CPT-2 deficiency, other family members can have DNA testing to see if they are carriers.

If DNA testing would not be helpful, other methods of carrier testing may be available. Your metabolic doctor or genetic counselor can answer your questions about carrier testing.

How many people have CPT-2 deficiency?

CPT-2 deficiency is rare. The actual incidence is unknown.

Does CPT-2 deficiency happen more often in a certain ethnic group?

CPT-2 deficiency does not happen more often in any specific race, ethnic group, geographical area or country.

Does CPT-2 deficiency go by any other names?

CPT-2 deficiency is also called:

Where can I find more information?

Fatty Oxidation Disorders (FOD) Family Support Group
http://www.fodsupport.org

Organic Acidemia Association
http://www.oaanews.org

United Mitochondrial Disease Foundation
http://www.umdf.org

Genetic Alliance
http://www.geneticalliance.org

Mito Action
http://www.mitoaction.org

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DISCLAIMER:

THIS INFORMATION DOES NOT PROVIDE MEDICAL ADVICE. All content ("Content"), including text, graphics, images and information are for general informational purposes only. You are encouraged to confer with your doctor or other health care professional with regard to information contained on this information sheet. After reading this information sheet, you are encouraged to review the information carefully with your doctor or other healthcare provider. The Content is not intended to be a substitute for professional medical advice, diagnosis or treatment. NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE, OR DELAY IN SEEKING IT, BECAUSE OF SOMETHING YOU HAVE READ ON THIS INFORMATION SHEET. This project is supported by a grant from the Maternal and Child Health Bureau, Health Resources and Service Administration, Genetic Services Branch, MCH Project #:1H46 MC 00189-03 http://mchb.hrsa.gov

Fact Sheet was last updated on: 7/13/13