Conditions Carnitine Acylcarnitine Translocase Deficiency

Carnitine acylcarnitine translocase deficiency (CACT) is a condition in which the body is unable to break down certain fats. It is considered a fatty acid oxidation condition because people affected by CACT are unable to break down some of the fats they eat into energy the body needs to function. This can cause too many unused fatty acids build up in the body. Detecting the condition early and beginning treatment can help prevent some of the severe outcomes of CACT.

Condition Type

Fatty Acid Oxidation Disorders


Carnitine acylcarnitine translocase deficiency (CACT) is very rare. At least 30 cases have been reported. However, the exact number of people affected by CACT is unknown.

Also known as

  • CACT
  • Carnitine acylcarnitine carrier deficiency
  • CAC
  • CACT deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of CACT (see Early Signs below). If your baby has certain signs, your baby’s doctor may suggest starting immediate treatment.

If your baby’s newborn screening result for carnitine acylcarnitine translocase deficiency (CACT) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated CACT can occur soon after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve checking your baby’s urine and blood samples for harmful amounts of acids and toxins. Certain acids and toxins build up in the body when a child has a fatty acid oxidation condition, so measuring the amounts of these substances in your baby’s body can help doctors determine if your baby has a condition. A high amount of C16 and/or C18:1 acylcarnitines in the blood may be a sign of CACT. Because the signs for CACT are similar to the signs for another fatty acid oxidation condition known as carnitine palmitoyltransferase II (CPT-II), your baby’s doctor may need to test a small skin sample to determine if your baby has either condition.

About Carnitine Acylcarnitine Translocase Deficiency

Early Signs

There are two main forms of carnitine acylcarnitine translocase deficiency (CACT), which differ by their age of onset: CACT in newborns and CACT in children. The signs of CACT are the same for these two forms.

Signs of CACT include:

  • Sleeping longer or more often
  • Behavior changes
  • Irritability
  • Poor appetite
  • Fever
  • Diarrhea
  • Vomiting
  • Low blood sugar (known as hypoglycemia)
  • Weak muscle tone (known as hypotonia)
  • Seizures (epilepsy)
  • Trouble breathing

Many of these signs may occur when your baby eats foods that their body cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.


Dietary Treatments

Your baby may need to be on a restricted diet in order to avoid certain foods that their body cannot break down. A nutritionist or dietician can help you plan a healthy diet for your baby (see Accessing Care).

Eating often can also help avoid many of the signs mentioned in the Early Signs section.

Supplements and Medication

Children with carnitine acylcarnitine translocase deficiency (CACT) often take a supplement called Medium Chain Triglyceride (MCT) oil. This oil contains fats that individuals with CACT can break down for energy. Talk to your baby’s doctor before starting this type of treatment.

Your baby’s doctor might also prescribe L-carnitine supplements for your baby. L-carnitine is a substance naturally made by the body, but your baby’s body might not make enough of it. Taking prescription L-carnitine supplements can help your baby break down fats for energy and remove harmful substances from the body.

Expected Outcomes

If carnitine acylcarnitine translocase deficiency (CACT) is identified early, treatment can help prevent or control many of the signs mentioned in the Early Signs section. This is why newborn screening is so important.

Even with treatment, babies are still at risk for an enlarged, weak heart, an enlarged liver, low blood sugar, coma, or death.

Babies who do not receive treatment for CACT usually die during infancy.


When we eat food, enzymes help break it down. Some enzymes help break down fats into their building blocks, called fatty acids. Other enzymes break down these fatty acids. In carnitine acylcarnitine translocase deficiency (CACT), the enzyme carnitine acylcarnitine translocase (CAT) is not working correctly.

CAT’s job is to help bring fatty acids into the mitochondria. Mitochondria are the energy-making factories of cells. When CAT is not working correctly, fatty acids cannot get inside of the mitochondria. This prevents fatty acids from being broken down for energy. Fatty acids are important sources of energy for the heart, especially when the body runs low on sugar (such as in between meals).

When fatty acids cannot be broken down, it also causes high levels of acid in the blood. Everyone has some acid in the blood, but too much acid can be toxic.

CACT is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for CACT, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with CACT is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Carnitine Acylcarnitine Translocase Deficiency

Support Services

Support groups can help connect families who have a child or other family member affected with carnitine acylcarnitine translocase deficiency (CACT) with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for affected individuals and their families, as well as health care providers.

Accessing Care

Work with your baby’s doctor to determine the next steps for your baby’s care. Your baby’s physician may help you coordinate care with a doctor who specializes in metabolism, a dietician who can help plan your child’s specialized diet, and other medical resources in your community. Depending on the symptoms of carnitine acylcarnitine translocase deficiency (CACT) that your child experiences, your baby’s doctor may work with other doctors who specialize in treating the heart or liver. Some children with CACT have developmental delays. If you think that your baby is not meeting their developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.

Because CACT is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for CACT, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the Amemrican College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

At this time we have not located a family story for this particular condition. If your family is affected by carnitine acylcarnitine translocase deficiency (CACT) and you would like to share your story, please contact us so other families may benefit from your experience.

Each family's experience with a condition is unique, but there are some parts of the evaluation and treatment of CACT that are similar to other fatty acid oxidation conditions. You may find it useful to read the stories of families affected by other fatty acid oxidation conditions on the family story page of the FOD Family Support Group website.

References & Sources

Visit the Screening, Technology And Research in Genetics (STAR-G) Project for more information on CACT

Visit MedlinePlus Genetics for more condition information

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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