Conditions Trifunctional Protein Deficiency

Trifunctional protein deficiency (TFP) 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 TFP are unable to change some of the fats they eat into energy the body needs to function. Instead, too many unused fatty acids build up in the body. Detecting TFP early and beginning treatment can often prevent some of the severe outcomes of TFP.

Condition Type

Fatty Acid Oxidation Disorders


Trifunctional protein deficiency (TFP) is a very rare condition. The exact number of individuals affected by TFP is currently unknown.

Also known as

  • TFP
  • Mitochondrial trifunctional protein deficiency
  • MTP deficiency
  • TFP deficiency
  • TPA deficiency
  • Type 2 trifunctional protein deficiency
  • Trifunctional enzyme deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of TFP (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 trifunctional protein deficiency (TFP) 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 TFP 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 levels of acids and toxins. Certain acids and toxins build up in the body when a child has an fatty acid oxidation condition, so measuring the levels of these substances in your baby’s body can help doctors determine if your baby has a condition. A specific pattern of acylcarnitines in the blood and organic acids in the urine might indicate that your baby has TFP. Because TFP has many of the same signs as another fatty acid oxidation condition called LCHAD, your baby’s doctor may order further testing to see if your baby has either condition. Sometimes follow-up testing may also include testing a very small sample of skin.

About Trifunctional Protein Deficiency

Early Signs

There are three distinct forms of trifunctional protein deficiency (TFP) based on the age of onset: early, childhood, and mild. If your baby has early TFP, you will start seeing signs between birth and age 2, whereas individuals with childhood TFP show signs after infancy. Mild TFP is very uncommon. If your child has mild TFP, their could start showing signs any time between 2 years of age and adulthood.

Signs of early TFP include:

  • Poor appetite
  • Sleeping longer or more often
  • Tiredness
  • Weak muscle tone (called hypotonia)
  • Fever
  • Vomiting
  • Diarrhea
  • Low blood sugar (called hypoglycemia)
  • Irritability
  • Behavior changes
  • No reflexes or pain responses
  • Developmental delays

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 childhood or mild TFP, check out the STAR-G’s website.


Your baby will need to be on a restricted diet in order to avoid certain high-fat foods that your baby’s body cannot break down. A dietician or a nutritionist can help you plan a diet that keeps your baby healthy while giving them the nutrients necessary for healthy growth.

Your baby will also need to eat often to avoid many of the signs mentioned in the Early Signs section.

Supplements and Medications

Your baby’s doctor might recommend supplements for your baby. Medium Chain Triglyceride (MCT) oil is a supplement that provides energy for your baby because it contains fatty acids that people with trifunctional protein deficiency (TFP) can digest. Talk to your baby’s doctor before starting this treatment.

Some children with TFP also take prescription L-carnitine supplements. L-carnitine is a substance that the body makes naturally, but your baby’s body might not make enough of it. Taking L-carnitine can help your baby with TFP break down fats and remove harmful substances from the body. Your baby’s doctor will need to write you a prescription for these supplements.

Lifestyle Changes

You will need to keep your baby out of extremely hot and cold temperatures. Extreme temperatures can promote muscle breakdown.

Expected Outcomes

If your child has childhood or mild trifunctional protein deficiency (TFP), they can live a healthy life with the help of treatment. Some children could still have hypoglycemic (low blood sugar) episodes, even with treatment.

Babies with early TFP may benefit from treatments. However, most babies are at risk of dying young from heart and breathing problems, even with treatment.

If TFP is not treated, hypoglycemic episodes can lead to coma or even death.


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.

Fatty acids are built like chains, and these chains come in various lengths. They are classified as either short, medium, long, or very long. Different enzymes are made to break down different length fatty acids. An enzyme complex (multiple enzymes attached to each other) called trifunctional protein helps break down “long” fatty acid chains. If you have a question about what makes a “long” fatty acid, check out this link.

If your baby has trifunctional protein deficiency (TFP), then their body either does not make enough or makes non-working trifunctional protein enzymes. This is harmful to the body because your baby’s heart and muscles need fatty acids for energy. Your baby’s body also needs to break down fatty acids when there is not enough sugar, such as between meals.

TFP is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for TFP, 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 TFP 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 Trifunctional Protein Deficiency

Support Services

Support groups can help connect people who have a child or other family member affected with trifunctional protein deficiency (TFP) 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 doctor may help you coordinate care with a doctor who specializes in metabolism, a dietician who can help plan your baby’s specialized diet, and other medical resources in your community. Depending on the signs and symptoms of your child’s trifunctional protein deficiency (TFP), your baby’s doctor may work with other doctors who specialize in treating the heart, lungs, or muscles to care for your child. Some children with TFP 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 TFP 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 TFP, 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

Each family's experience with a condition is unique, but there are some parts of the diagnosis, experience, and treatment of trifunctional protein deficiency (TFP) 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. The Save Babies through Screening Foundation publishes stories of families who have a child with a fatty acid oxidation condition. Read these family stories on their website.

If your family is affected by TFP 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 TFP deficiency

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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