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Carnitine-acylcarnitine translocase deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Carnitine-acylcarnitine translocase deficiency

Carnitine-acylcarnitine translocase (CACT) deficiency is a rare genetic condition that prevents the body from using certain fats for energy, particularly during periods without food. This disorder can lead to life-threatening complications, with symptoms often appearing shortly after birth.

Overview

Carnitine-acylcarnitine translocase (CACT) deficiency is a condition that prevents the body from using certain fats for energy, particularly during periods without food (fasting). Many infants with CACT deficiency do not survive the newborn period. However, some affected individuals have a less severe form of the condition and do not develop signs and symptoms until early childhood. These individuals remain at risk for liver failure, nervous system damage, coma, and sudden death.

Symptoms

Signs and symptoms of CACT deficiency usually begin soon after birth and can include:

  • Breathing problems
  • Seizures
  • An irregular heartbeat (arrhythmia)
  • Low blood glucose (hypoglycemia) combined with a low level of ketones (hypoketotic hypoglycemia)
  • Excess ammonia in the blood (hyperammonemia)
  • An enlarged liver (hepatomegaly)
  • A weakened heart muscle (cardiomyopathy)

Frequency

CACT deficiency is a very rare disorder; at least 30 cases have been reported in medical literature.

Causes & Genetic Factors

Mutations in the SLC25A20 gene cause CACT deficiency. This gene provides instructions for making a protein called carnitine-acylcarnitine translocase (CACT). This protein is essential for fatty acid oxidation, a multistep process that breaks down (metabolizes) fats and converts them into energy inside the mitochondria (the energy-producing centers in cells).

A group of fats called long-chain fatty acids must be attached to a substance known as carnitine to enter the mitochondria. Once joined, the CACT protein transports them inside. Fatty acids are a major source of energy for the heart and muscles, and they serve as an important energy source for the liver and other tissues during fasting.

Mutations in the SLC25A20 gene alter the structure of the CACT protein, leading to a shortage (deficiency) of the transporter. Without enough functional CACT protein, long-chain fatty acids cannot be transported into the mitochondria to be converted into energy. This reduced energy production leads to features like hypoketotic hypoglycemia. Additionally, fatty acids and long-chain acylcarnitines (fatty acids still attached to carnitine) can build up in cells, damaging the liver, heart, and muscles, which causes the other signs and symptoms of the disorder.

Associated Gene

  • SLC25A20

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • CACT deficiency
  • Carnitine acylcarnitine translocase deficiency
  • Carnitine-acylcarnitine carrier deficiency

Frequently Asked Questions

Parents should be vigilant for signs such as sudden difficulty breathing, new or worsening seizures, an irregular or very fast heartbeat, extreme lethargy, or signs of very low blood sugar like poor feeding, jitteriness, or unresponsiveness. These symptoms, especially during periods without food, indicate a metabolic crisis and require immediate emergency medical care to prevent serious complications like coma, liver failure, or sudden death.
Managing CACT deficiency primarily involves avoiding prolonged fasting, which can trigger a metabolic crisis. Infants and children typically require frequent feedings, often every 2-3 hours, with special diets that are low in long-chain fats and supplemented with medium-chain triglycerides. During illness or stress, it's crucial to ensure continuous glucose intake, sometimes through intravenous fluids, to provide an alternative energy source and prevent the body from relying on fat metabolism.
CACT deficiency is an autosomal recessive genetic condition, meaning a child must inherit two copies of a mutated SLC25A20 gene (one from each parent) to develop the disorder. Parents who each carry one copy of the mutated gene are typically unaffected but have a 25% chance with each pregnancy of having a child with CACT deficiency. Genetic counseling and testing are available for families to understand their risk and explore options for future pregnancies.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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