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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Carnitine palmitoyltransferase I deficiency

(often shortened to CPT I deficiency)
Reviewed April 2014

What is CPT I deficiency?

Carnitine palmitoyltransferase I (CPT I) deficiency is a condition that prevents the body from using certain fats for energy, particularly during periods without food (fasting). The severity of this condition varies among affected individuals.

Signs and symptoms of CPT I deficiency often appear during early childhood. Affected individuals usually have low blood sugar (hypoglycemia) and a low level of ketones, which are produced during the breakdown of fats and used for energy. Together these signs are called hypoketotic hypoglycemia. People with CPT I deficiency can also have an enlarged liver (hepatomegaly), liver malfunction, and elevated levels of carnitine in the blood. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Individuals with CPT I deficiency are at risk for nervous system damage, liver failure, seizures, coma, and sudden death.

Problems related to CPT I deficiency can be triggered by periods of fasting or by illnesses such as viral infections. This disorder is sometimes mistaken for Reye syndrome, a severe disorder that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome are associated with the use of aspirin during these viral infections.

How common is CPT I deficiency?

CPT I deficiency is a rare disorder; fewer than 50 affected individuals have been identified. This disorder may be more common in the Hutterite and Inuit populations.

What genes are related to CPT I deficiency?

Mutations in the CPT1A gene cause CPT I deficiency. This gene provides instructions for making an enzyme called carnitine palmitoyltransferase 1A, which is found in the liver. Carnitine palmitoyltransferase 1A is essential for fatty acid oxidation, which is the multistep process that breaks down (metabolizes) fats and converts them into energy. Fatty acid oxidation takes place within mitochondria, which are the energy-producing centers in cells. A group of fats called long-chain fatty acids cannot enter mitochondria unless they are attached to carnitine. Carnitine palmitoyltransferase 1A connects carnitine to long-chain fatty acids so they can enter mitochondria and be used to produce energy. During periods of fasting, long-chain fatty acids are an important energy source for the liver and other tissues.

Mutations in the CPT1A gene severely reduce or eliminate the activity of carnitine palmitoyltransferase 1A. Without enough of this enzyme, carnitine is not attached to long-chain fatty acids. As a result, these fatty acids cannot enter mitochondria and be converted into energy. Reduced energy production can lead to some of the features of CPT I deficiency, such as hypoketotic hypoglycemia. Fatty acids may also build up in cells and damage the liver, heart, and brain. This abnormal buildup causes the other signs and symptoms of the disorder.

Related Gene(s)

Changes in this gene are associated with carnitine palmitoyltransferase I deficiency.

  • CPT1A

How do people inherit CPT I deficiency?

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.

Where can I find information about diagnosis or management of CPT I deficiency?

These resources address the diagnosis or management of CPT I deficiency and may include treatment providers.

  • Baby's First Test (
  • FOD (Fatty Oxidation Disorders) Family Support Group: Diagnostic Approach to Disorders of Fat Oxidation - Information for Clinicians (
  • Gene Review: Carnitine Palmitoyltransferase 1A Deficiency (
  • Genetic Testing Registry: Carnitine palmitoyltransferase I deficiency (

You might also find information on the diagnosis or management of CPT I deficiency in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about CPT I deficiency?

You may find the following resources about CPT I deficiency helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for CPT I deficiency?

  • carnitine palmitoyltransferase IA deficiency
  • CPT 1A deficiency
  • CPT deficiency, hepatic, type I
  • liver form of carnitine palmitoyltransferase deficiency

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about CPT I deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding CPT I deficiency?

acids ; autosomal ; autosomal recessive ; breakdown ; carnitine ; cell ; coma ; deficiency ; enzyme ; fasting ; fatty acids ; gene ; hepatic ; hypoglycemia ; inherited ; liver failure ; mitochondria ; nervous system ; newborn screening ; oxidation ; recessive ; screening ; syndrome

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Akkaoui M, Cohen I, Esnous C, Lenoir V, Sournac M, Girard J, Prip-Buus C. Modulation of the hepatic malonyl-CoA-carnitine palmitoyltransferase 1A partnership creates a metabolic switch allowing oxidation of de novo fatty acids. Biochem J. 2009 May 27;420(3):429-38. doi: 10.1042/BJ20081932. (
  • Bennett MJ, Boriack RL, Narayan S, Rutledge SL, Raff ML. Novel mutations in CPT 1A define molecular heterogeneity of hepatic carnitine palmitoyltransferase I deficiency. Mol Genet Metab. 2004 May;82(1):59-63. (
  • Dykema DM. Carnitine palmitoyltransferase-1A deficiency: a look at classic and arctic variants. Adv Neonatal Care. 2012 Feb;12(1):23-7. doi: 10.1097/ANC.0b013e318242df6d. (
  • Gobin S, Thuillier L, Jogl G, Faye A, Tong L, Chi M, Bonnefont JP, Girard J, Prip-Buus C. Functional and structural basis of carnitine palmitoyltransferase 1A deficiency. J Biol Chem. 2003 Dec 12;278(50):50428-34. Epub 2003 Sep 29. (
  • Greenberg CR, Dilling LA, Thompson GR, Seargeant LE, Haworth JC, Phillips S, Chan A, Vallance HD, Waters PJ, Sinclair G, Lillquist Y, Wanders RJ, Olpin SE. The paradox of the carnitine palmitoyltransferase type Ia P479L variant in Canadian Aboriginal populations. Mol Genet Metab. 2009 Apr;96(4):201-7. doi: 10.1016/j.ymgme.2008.12.018. Epub 2009 Feb 13. (
  • Longo N, Amat di San Filippo C, Pasquali M. Disorders of carnitine transport and the carnitine cycle. Am J Med Genet C Semin Med Genet. 2006 May 15;142C(2):77-85. Review. (
  • Olpin SE, Allen J, Bonham JR, Clark S, Clayton PT, Calvin J, Downing M, Ives K, Jones S, Manning NJ, Pollitt RJ, Standing SJ, Tanner MS. Features of carnitine palmitoyltransferase type I deficiency. J Inherit Metab Dis. 2001 Feb;24(1):35-42. (
  • Rajakumar C, Ban MR, Cao H, Young TK, Bjerregaard P, Hegele RA. Carnitine palmitoyltransferase IA polymorphism P479L is common in Greenland Inuit and is associated with elevated plasma apolipoprotein A-I. J Lipid Res. 2009 Jun;50(6):1223-8. doi: 10.1194/jlr.P900001-JLR200. Epub 2009 Jan 29. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: April 2014
Published: February 8, 2016