CAT (carnitine/acylcarnitine translocase deficiency)
FATTY ACID DISORDER
Disorder name: Carnitine acylcarnitineOur bodies break down the fat that we eat into substances called fatty acids. Fatty acids are then broken down even further into substances called acylcarnitines. Acylcarnitines are used to create energy for the body. translocase deficiency
- What is CAT deficiency?
- What causes CAT deficiency?
- If CAT deficiency is not treated, what problems occur?
- What is the treatment for CAT deficiency?
- What happens when CAT deficiency is treated?
- What causes the CAT enzyme to be absent or not working correctly?
- How is CAT deficiency inherited?
- Is genetic testing available?
- What other testing is available?
- Can you test during a future pregnancy?
- Can other members of the family have CAT deficiency or be carriers?
- Can other family members be tested?
- How many people have CAT deficiency?
- Does CAT deficiency happen more often in a certain ethnic group?
- Does CAT deficiency go by any other names?
- Where can I find more information?
This fact sheet has general information about CAT deficiency. Every child is different and some of this information may not apply to your child specifically. Not all is known about CAT deficiency and, at present, there is no standard treatment plan. There may be treatments recommended for some children but not others. Children with CAT deficiency should be followed by a metabolic doctor in addition to their primary doctor.
WHAT IS CAT DEFICIENCY?
CAT deficiency stands for “carnitine acylcarnitine translocase deficiency.” It is one type of fatty acid oxidationThis is the process used by the body to change fatty acids, the building blocks of fat, into energy. It happens in the mitochondria – the small energy-producing parts found in each cell of the body. disorder. People with CAT deficiency have problems breaking down fat into energy for the body.
|Fatty Acid Oxidation Disorders:
Fatty acid oxidation disorders (FAODs)This is a group of rare inherited conditions. FAODs are caused by missing or non-working enzymes. Normally, many enzymes are used by the body to break down fat into energy. In people with FAODs, one of these enzymes is not working and fat cannot be used for energy. If these conditions are not treated, they can lead to serious health problems. are a group of rare inheritedAcquiring a trait from one’s parents. Most traits, such as eye color or hair color, are inherited from a parent through genes. conditions. They are caused by enzymes that do not work properly.
A number of enzymesA molecule that helps chemical reactions take place. For example, enzymes in the stomach speed up the process of breaking down food. Each enzyme can participate in many chemical reactions without changing or being used up. 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 fatFat is one of the three main nutrients in food (carbohydrates, fat, protein). Some foods that contain fat are butter, margarine, oils, nuts, meats, poultry, fish and some dairy products. Extra calories from food are stored as body fat. Stored body fat provides the body with a reserve supply of energy. 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 CAT DEFICIENCY?
CAT deficiency occurs when an enzyme, called “carnitine acylcarnitine translocase” (CAT), 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 to break down fat already stored in the body.
Energy from fat keeps us going whenever our bodies run low of their main source of energy, a type of sugar called glucoseThis is a type of sugar made from the carbohydrates in food. Glucose is found in the blood. It is the main source of energy for the body and brain.. Our bodies rely on fat for energy when we don’t eat for a stretch of time – like when we miss a meal or when we sleep.
When the CAT 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 hypoglycemiaThis happens when there is too little sugar (glucose) in the blood. It may cause a person to feel nervous, shaky, weak, or sweaty. It may also cause headache, blurred vision, and hunger. If left untreated, it can cause unconsciousness (coma) and sometimes even death., and to the build up of harmful substances in the blood.
IF CAT DEFICIENCY IS NOT TREATED, WHAT PROBLEMS OCCUR?
CAT deficiency can cause episodes of illness called metabolic crises. Some of the first symptoms of a metabolic crisisThis is a serious health condition caused by low blood sugar and the build-up of toxic substances in the blood. Symptoms of a metabolic crisis are poor appetite, nausea, vomiting, diarrhea, extreme sleepiness, irritable mood and behavior changes. If not treated, breathing problems, seizures, coma, and sometimes even death can occur.Metabolic crises happen more often in people with certain metabolic disorders (some fatty acid oxidation disorders, amino acid disorders, and organic acid disorders). They are often triggered by things like illness or infection, going without food for a long time, and, in some cases, heavy exercise. are:
- extreme sleepiness
- behavior changes
- irritable mood
- poor appetite
Other symptoms then follow:
If a metabolic crisis is not treated, a child with CAT deficiency can develop:
- muscle weakness
- seizuresThese are also called "convulsions" or "fits." During a seizure, a person loses consciousness and control of his or her muscles. It may also cause involuntary movements. Seizures can happen for many reasons. Some causes are metabolic disorders, a metabolic crisis, brain injury, and infection.
- breathing problems
- comaThis is a sleep-like condition from which a person cannot be awakened. People in a coma are unconscious. A coma can be caused by many things. Two causes are untreated low blood sugar (hypoglycemia) and a metabolic crisis., sometimes leading to death
There are two types of CAT deficiency. The most common type happens in newborns. A milder, less common type happens in older infants and children.
CAT deficiency in newborns
Newborns with CAT deficiency often show symptoms within the first week of life. Episodes of metabolic crisis are common. High levels of ammonia in the blood can occur. This can cause serious brain damage.
Newborns with CAT may also have:
- low muscle tone (floppy muscles and joints) and muscle weakness
- enlarged liver
- heart problems and enlarged heart
- breathing problems
Babies who are not treated usually die of heart problems, breathing problems, liver failure, or high levels of ammoniaThis is a waste product made when protein is broken down for the body to use. Ammonia is harmful to the body. It is usually changed to a harmless substance called “urea.” Urea is then removed from the body in the urine. People with urea cycle disorders cannot get rid of ammonia. If these conditions are not treated, ammonia can build up and cause serious health problems. in the blood.
CAT deficiency in children
Children with the mild type of CAT deficiency usually start having symptoms before age three. They are at risk to have episodes of metabolic crisis, but usually do not have heart problems.
In both types of CAT deficiency, symptoms often happen after having nothing to eat for more than a few hours. Symptoms are also more likely when a person with CAT deficiency gets sick or has an infection.
WHAT IS THE TREATMENT FOR CAT DEFICIENCY?
Your baby’s primary doctor will work with a metabolic doctorThis is a doctor or medical geneticist who has special training in diagnosing and treating metabolic disorders. They often work in university hospitals or large medical centers. to care for your child. Your doctor may also suggest that you meet with a dietician familiar with CAT deficiency.
Certain treatments may be helpful for some children but not others. When necessary, treatment is usually needed throughout life. The following are treatments sometimes recommended for children with CAT deficiency:
1. Avoid going a long time without food
Infants and young children with CAT 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 dieticianThis is a person with special training in food and nutrition. A registered dietician (RD) has met the necessary educational requirements and has passed a national examination. If your child has a metabolic disorder, it is important for you to work with a registered dietician. They help create healthy food plans for people with metabolic disorders or other special needs. 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 CAT deficiency can go without food for up to 12 hours without problems. The other treatments usually need to be continued throughout life.
Sometimes a low-fat, high carbohydrate diet is advised. In fact, for children needing this treatment, most foods in the diet should be carbohydratesThis is one of the three types of nutrients in food (carbohydrates, fats, proteins). Sugars and starches are the most important types of carbohydrates. They are broken down by the body into glucose, the main source of energy for the body. Carbohydrates are found in foods such as: bread, cereal, pasta, grains, fruits and vegetables. Milk and dairy products, fruit drinks, sugar, candy, and sweet desserts also contain carbohydrates. (bread, pasta, fruit, vegetables, etc.) and protein (lean meat and low-fat dairy food).
People with CAT deficiency cannot use particular building blocks of fat called “long-chain fatty acidsThis is one of many types of fatty acids, the building blocks of fat. Long-chain fatty acids are made up of chains of 12 or more carbon atoms..” A dietician can help you create a food plan low in these fats. Any diet changes should be made under the guidance of a dietician experienced with CAT deficiency.
Ask your doctor whether your child needs to have any changes in his or her diet.
3. Medium Chain Triglycerides
Medium Chain Triglycerides (MCT) are often used as part of the food plan for people with CAT deficiency. MCTs are available in MCT oil and in triheptanoin (DOJOLVI ®) – a medication made of MCTs. These supplements have medium chain fatty acidsThis is one of many types of fatty acids, the building blocks of fat. Medium-chain fatty acids are made up of chains of 4 to 12 carbon atoms. that can be used in small amounts for energy. Your metabolic doctor or dietician can tell you how to use these supplements. You will need to get a prescription from your doctor to get these MCTs supplements.
4. L-carnitineThis is a natural substance found in muscle cells. It helps the body make energy from the fat in food and the fat stored in the body. It also helps the cells get rid of harmful wastes made during the breakdown of fat. Carnitine supplements may be used as a treatment for some metabolic disorders.
Some children may be helped by taking L-carnitine. This is a safe and natural substance that helps body cellsThe smallest living unit. Cells make up all organs and tissues in multi-cellular organisms, like humans. They can also live independently, as in bacteria and other microorganisms. At a minimum, a cell is surrounded by a membrane, contains DNA at some stage in its life, and is able to replicate itself into two equal parts. 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 L-carnitine without checking with your doctor.
5. Call your doctor at the start of any illness
Always call your health care provider when your child has any of the following:
- poor appetite
- low energy or excessive sleepiness
- an infection
- a fever
- persistent muscle pain or weakness
Children with CAT deficiency need to eat extra starchy food and drink more fluids during any illness – even if they may not feel hungry – or they could develop a metabolic crisis. Children who are sick often don’t want to eat. If they won’t or can’t eat, children with CAT deficiency 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.
WHAT HAPPENS WHEN CAT DEFICIENCY IS TREATED?
Prompt and careful treatment may help prevent or control symptoms in children with CAT deficiency. However, some children continue to have metabolic crises and other health problems despite treatment. Even with treatment, there is a risk of death, especially in newborns with symptoms.
WHAT CAUSES THE CAT ENZYME TO BE ABSENT OR NOT WORKING CORRECTLY?
Genes tell the body to make various enzymes. The SLC25A20 gene instructs the body to make the enzyme carnitine-acylcarnitine translocase (CAT enzyme). Everyone has two copies of the SLC25A20 gene. People with CAT deficiency have changes, also called variantsA variant is a change or alteration in a person’s DNA sequence. Variants can happen in genes and affect how the gene functions. There are different types of variants – they can be non-problem causing (benign), disease-causing (pathogenic) or of unknown significance. The term variants is now used in place of the term mutation. in both copies of their SLC25A20 genesA segment of DNA that contains the instructions to make a specific protein (or part of a protein). Genes are contained on chromosomes. Chromosomes, and the genes on those chromosomes, are passed on from parent to child. Errors in the DNA that make up a gene are called variants and can lead to diseases. that cause them to not work correctly. Because of the variants in the SLC25A20 genes, the CAT enzyme either does not work properly or is not made at all.
HOW IS CAT DEFICIENCY INHERITED?
CAT deficiency is inherited in an autosomal recessive manner. It affects both boys and girls equally.
Everyone has two copies of the SLC25A20 gene that makes the CAT enzyme. In children with CAT deficiency, neither of these genes works correctly. These children inherit one non-working SLC25A20 gene for the condition from each parent.
Parents of children with CAT deficiency rarely have the disorder. Instead, each parent has a single non-working SLC25A20 gene for CAT deficiency. They are called carriersA person who has one copy of a gene mutation for a particular autosomal recessive disorder (remember genes come in pairs). Carriers are not affected by the disorder. However, they can pass on the gene variant to their children. Children who inherit two such gene variants will be affected by the disorder. The term variants is now used in place of the term mutation.. Carriers do not have the condition because their other SLC25A20 gene is working correctly.
When both parents are carriers, there is a 25% chance in each pregnancy for the child to have CAT 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 have two working genes.
GeneticRelating to (or due to) genes and heredity or the field of studying genes and heredity. counseling is available to families who have children with CAT deficiency. Genetic counselors can answer your questions about how CAT deficiency is inherited, options during future pregnancies, and how to test other family members. Ask your doctor about a referral to a genetic counselorThese are health care providers who have special training in genetic conditions. They help families understand genetic disorders and how they are passed down. Genetic counselors offer information and support to people who have genetic conditions in their families or are concerned that they may have a child with an inherited disorder..
IS GENETIC TESTING AVAILABLE?
Genetic testing for CAT deficiency can be done on a blood sample. Genetic testing, also called DNA testing, looks for changes (variants) in the SLC25A20 genes that cause CAT deficiency.
DNADeoxyribonucleic acid (DNA) is a molecule found in the chromosomes that carries genetic information. DNA is composed of four units (called bases) that are designated A, T, G, and C. The sequence of the bases spell out instructions for making all of the proteins needed by an organism. A gene is a section of DNA that holds the instructions for a specific protein. A change in one or more of the DNA bases making up a gene is called a mutation. Some mutations change the protein instructions and can lead to particular health problems or disorders. Each parent passes half of their chromosomes, and thus half of their DNA instructions, onto their children. It is these instructions that cause certain traits, such as eye or hair color, to be inherited. 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?
CAT deficiency can also be confirmed by a special enzyme test on a skin sample. Talk to your doctor or genetic counselor if you have questions about testing for CAT deficiency.
CAN YOU TEST DURING A FUTURE PREGNANCY?
If both gene changes (variants) have been found in the child with CAT deficiency, DNA testing can be done during future pregnancies. The sample needed for this test is obtained by either CVS or amniocentesisThis is a test done during pregnancy. A needle is used to remove a small sample of fluid from the sac around the fetus. The sample can be used to test for certain genetic disorders in the fetus. Amniocentesis to test for genetic conditions is usually done between 13 and 20 weeks of pregnancy..
If DNA testing would not be helpful, testing during pregnancy can be attempted by performing special tests on fetal cells. Again, the sample needed for these tests is obtained by either CVSThis is a special test done early in pregnancy. During CVS, a small sample of the placenta is removed for testing. This sample can be used to test for certain genetic disorders in the fetus. CVS is usually done between 10 and 12 weeks of pregnancy. or amniocentesis.
Parents may either choose to have testing during pregnancy or wait until birth. Parents may also choose to use assisted reproductive techniques to decrease the chance that their future children would have CAT deficiency. A genetic counselor can talk to you about your choices and answer other questions about prenatal testing or testing your baby after birth.
CAN OTHER MEMBERS OF THE FAMILY HAVE CAT DEFICIENCY OR BE CARRIERS?
The brothers and sisters of an affected baby have a chance of having CAT deficiency, even if they haven’t had symptoms. Finding out whether other children in the family have CAT deficiency is important because early treatment may prevent serious health problems. Talk to your doctor or genetic counselor about testing your other children.
CAT deficiency carriers
Brothers and sisters who do not have CAT 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.
If you are a parent of a child with CAT deficiency, your brothers and sisters have a 50% chance to be a 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 CAT deficiency.
Some states do not offer newborn screening for CAT deficiency. However, expanded newborn screeningA screening test that looks for different disorders using a small sample of blood taken from a newborn’s heel. A positive or abnormal newborn screening result means that there are slight differences that were found in the baby’s blood, and further testing is needed to figure out if the baby has a metabolic disorder. is available through private labs for babies born in states that do not screen for this condition. Your healthcare provider or genetic counselor can help you obtain expanded newborn screeningThe process of testing for disease in a person who does not show signs of having the disease (nonsymptomatic or asymptomatic person). The goal of screening is to catch the disease in its early stages..
When both parents are carriers, newborn screening results are not sufficient to rule out CAT 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 CAT deficiency may be at increased risk to develop serious medical problems. Some women carrying fetuses with Fatty Acid Oxidation Disorders have developed:
- excessive vomiting
- abdominal pain
- high blood pressure
- jaundiceThis is a yellow color to the skin and whites of the eyes. It is often a sign of liver damage.
- abnormal fat storage in the liver
- severe bleeding
All women with a family history of CAT 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 for CAT deficiency
Brothers and sisters of an affected child can be tested for CAT deficiency using either DNA testing or a special enzyme test to determine if they also have this disorder.
If both gene changes in the SLC25A20 genes have been found in the child with CAT 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 CAT DEFICIENCY?
CAT deficiency is very rare. The incidence in the United States in thought to be between 1 in 750,000 to 1 in 2,000,000. The incidence in Asian is thought to be between 1 in 60,000 and 1 in 400,000.
DOES CAT DEFICIENCY HAPPEN MORE OFTEN IN A CERTAIN ETHNIC GROUP?
No, CAT deficiency does not happen more often in any specific race, ethnic group, geographical area, or country.
DOES CAT DEFICIENCY GO BY ANY OTHER NAMES?
CAT deficiency is also known as:
- carnitine acylcarnitine carrier (CAC)
- CACT deficiency
WHERE CAN I FIND MORE INFORMATION?
Fatty Oxidation Disorders (FOD) Family Support Group
Organic Acidemia Association
United Mitochondrial Disease Foundation
Metabolic Support UK
Baby’s First Test
|Reviewed by:||HI, CA, OR, and WA metabolic specialists|
|Review date:||September 31, 2007
June 30, 2013
March 1, 2023
|Update on:||March 1, 2023|
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