Conditions Carnitine Palmitoyltransferase Type II Deficiency

Carnitine palmitoyltransferase type II deficiency (CPT-II) 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 with CPT-II are unable to change some of the fats they eat into energy the body needs to function. This can cause too many unused fatty acids to build up in the body. The health outcomes and treatment of CPT-II depend on the age of onset. Detecting the condition early and beginning treatment can often prevent many of the severe health outcomes of CPT-II.

Condition Type

Fatty Acid Oxidation Disorders


Carnitine palmitoyltransferase type II deficiency (CPT-II) is a rare condition. There are three main forms of CPT-II, which differ in their age of onset. The neonatal form has been reported in 18 cases. The form that affects babies and young children has been described in at least 30 cases. Classic CPT-II generally affects adults, and it is the most common form. It has been reported in more than 300 cases. The overall incidence of CPT-II is unknown.

Also known as

  • CPT-II
  • CPT-2 deficiency
  • Carnitine palmyitoyl transferase II deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of CPT-II (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 palmitoyltransferase type II deficiency (CPT-II) 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 CPT-II 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 child has a condition. High amounts of C16 and/or C18:1 acylcarnitines in the blood and lactic acid and dicarboxylic acids in the urine may be signs of CPT-II. The signs for CPT-II are similar to the signs for another fatty acid oxidation condition known as CACT, so your baby’s doctor may need to test a small skin sample to determine if your baby has either condition.

About Carnitine Palmitoyltransferase Type II Deficiency

Early Signs

There are three main forms of carnitine palmitoyltransferase type II deficiency (CPT-II), which differ in their age of onset: an extremely severe form in newborns (neonatal), a severe form in babies and young children, and a mild form in adults. Most individuals with CPT-II have the “classic” adult form. Classic CPT-II has different signs than CPT-II in babies or children.

Signs of CPT-II in babies include:

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

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.

If you are interested in information about the signs of classic CPT-II, check out the STAR-G’s site.


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 dietician or a nutritionist can help you plan a healthy diet for your child.

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

Supplements and Medications

Medium Chain Triglyceride (MCT) oil supplements are a common treatment for carnitine palmitoyltransferase type II deficiency (CPT-II). MCT oil contains fatty acids that individuals with CPT-II can break down for energy. Talk to your baby’s doctor before starting this type of treatment.

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

Lifestyle Changes

Your baby may need to avoid the cold because cold weather can trigger some signs of CPT-II, such as muscle weakness (see Early Signs).

Expected Outcomes

Children who are treated early for carnitine palmitoyltransferase type II deficiency (CPT-II) can have healthy growth and development. This is why newborn screening is so important. Adults who receive treatment can also lead healthy lives.

Some babies and children who receive treatment may develop some heart, kidney, and liver troubles that are commonly associated with CPT-II.

Babies and children who are not treated for CPT-II are at risk of severe heart, liver, and kidney trouble, brain damage or early death. Adults who are not treated for CPT-II often experience kidney failure.


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 palmitoyltransferase type II deficiency (CPT-II), the enzyme carnitine palmitoyltransferase II is not working correctly.

This enzyme’s job is to prepare fatty acids to be broken down inside of the mitochondria. Mitochondria are the energy making factories of cells. A special enzyme, called carnitine, helps bring fatty acids into the mitochondria. The fatty acids cannot enter unless they are attached to carnitine. Once inside, carnitine palmitoyltransferase II removes carnitine so the fatty acid can be broken down for energy.

Individuals with CPT-II cannot remove carnitine from the fatty acids in the mitochondria, so they cannot break down fatty acids for energy. Fatty acids are important sources of energy for the heart, especially when sugars are low, such as between meals.

CPT-II is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for CPT-II, 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 CPT-II 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 Palmitoyltransferase Type II Deficiency

Support Services

Support groups can help connect families who have a child or other family member affected with carnitine palmitoyltransferase type II deficiency (CPT-II) 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 your baby experiences, your baby’s doctor may work with other doctors who specialize in treating the heart, kidneys, or muscles. Some children with carnitine palmitoyltransferase type II deficiency (CPT-II) 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 CPT-II 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 CPT-II, 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 American 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

While there are many family stories available for the adult-onset form of carnitine palmitoyltransferase type II deficiency (CPT-II), we have not yet located a family story for the form of this condition that affects babies. If your family is affected by CPT-II and you would like to share your story, please contact us so other families may learn from your experience.

References & Sources

Visit MedlinePlus Genetics for more condition information

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

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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