Carnitine Palmitoyltransferase 1A (CPT 1) Deficiency

Guidance for primary care clinicians receiving a positive newborn screen result

Other Names

Carnitine palmitoyltransferase deficiency, type 1A (CPT1)
Carnitine palmitoyltransferase 1 deficiency

ICD-10 Coding

E71.314, Muscle carnitine palmitoyltransferase deficiency

Disorder Category

Fatty acid oxidation disorder


Abnormal Finding

Elevated C0 and C0/(C16+C18) ratio

Tested By

Tandem mass spectrometry (MS/MS); sensitivity=100%; specificity=N/A% [Schulze: 2003]


Carnitine palmitoyltransferase 1A (CPT1) is a mitochondrial enzyme involved in the conjugation of fatty acids to carnitine for subsequent transfer inside mitochondria through the action of a translocase. Variants in the CPT1A gene cause CPT1 deficiency. Deficient CPT1 activity results in impaired energy production, which usually manifests during prolonged fasting and/or increased energy demands (fever, stress), resulting in acute hepatic encephalopathy and hypoketotic hypoglycemic crises. CPT1A is predominantly expressed in the liver; therefore, unlike other fatty acid oxidation disorders, the muscle and heart are not primarily affected. Acute fatty liver of pregnancy may occur in a heterozygous mother of an affected fetus. Presentation in the neonatal period is rare.

Clinical Characteristics

With treatment, CPT1 deficient patients may be able to avoid episodes of acute liver failure and hypoglycemia, though it can still occur during times of metabolic stress.
Without treatment, neonates may experience life-threatening hepatic encephalopathy and hypoglycemia with subsequent risk for long-term neurologic damage.
Initial signs/symptoms of CPT1 deficiency typically begin suddenly in association with an illness and/or prolonged fasting and may be life-threatening. They usually include:
  • Poor appetite
  • Vomiting
  • Lethargy
  • Lab findings:
    • Hyperammonemia
    • Elevated transaminases
    • Metabolic acidosis
    • Hypoglycemia


CPT1 is rare, with an estimated prevalence of 1:500,000 to 1:1,000,000 newborns. [Bennet: 2016] There is a specific arctic variant (CPT1A p.P479L) common in Inuit populations of Alaska and Canada that has a much more mild phenotype.


Autosomal recessive

Primary Care Management

Next Steps After a Positive Screen

  • Contact the family to inform them of the positive result and ask if the infant has shown signs of lethargy, poor feeding, or seizures.
  • Consult with a pediatric metabolic specialist immediately.
  • Evaluate the newborn for lethargy, liver disease, or seizures. If any of these signs are present or the newborn is ill, transport to a hospital for further treatment with help from the metabolic specialist.
  • Initiate confirmatory/diagnostic testing and management, as recommended by the specialist (see below).

Confirming the Diagnosis

  • To confirm the diagnosis of CPT1, work with Newborn Screening Services (see NM providers [3]).
  • Additional testing may include glucose, blood gas, electrolytes, liver function tests, ammonia level, quantitative plasma acylcarnitine profile, enzyme activity assay in cultured fibroblasts, and CPT1A gene sequencing. The increased C0/(C16+C18) ratio is better detected from the dried blood spot collected for newborn screening. In plasma, C0 can be only mildly increased with low levels of C16 and C18.

If the Diagnosis is Confirmed

  • For evaluation and ongoing collaborative management, consult Biochemical Genetics (Metabolics) (see NM providers [1]).
  • Educate the family regarding signs, symptoms, and the need to avoid fasting and seek urgent care when the infant becomes ill. See CPT1 Deficiency - Information for Parents (STAR-G) for additional information.
  • Provide a letter and, when old enough, a MedicAlert bracelet indicating the risk for hypoglycemia and need for urgent treatment with IV glucose when illness or stress leads to symptoms.
  • Provide frequent, low-fat, and high-carbohydrate meals and snacks. In some cases, cornstarch is added to meals.
  • Medium-chain triglyceride oil supplements may be indicated for some children.
Assist in management, particularly with developmental and educational interventions for those identified after irreversible consequences. Refer to Early Intervention for Children with Disabilities/Delays (see NM providers [34]) as needed.


Information & Support

Related Portal Content
Fatty Acid Oxidation Disorders (FAQ)
Answers to frequently asked questions about a diagnosis of a fatty acid oxidation disorder.
After a Diagnosis or Problem is Identified
Families can face a big change when their baby tests positive for a newborn condition. Find information about A New Diagnosis - You Are Not Alone; Caring for Children with Special Health Care Needs; Assistance in Choosing Providers; Partnering with Healthcare Providers; Top Ten Things to Do After a Diagnosis.
Affording Formula
Tips for finding discounted formula and supplementation.

For Professionals

CPT1 Deficiency (GeneReviews)
Detailed information addressing clinical characteristics, diagnosis/testing, management, genetic counseling, and molecular pathogenesis; from the University of Washington and the National Library of Medicine.

For Parents and Patients

CPT1 Deficiency - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received an initial diagnosis of this newborn disorder; Screening, Technology and Research in Genetics.

Fatty Oxidation Disorders (FOD) Family Support Group
Information for families about fatty acid oxidation disorders, support groups, coping, finances, and links to other sites.


ACT Sheet for Carnitine Palmitoyltransferase I (CPT I) Deficiency (ACMG)
Provides recommendations for clinical and laboratory follow-up of the newborn with out-of-range screening results, along with national resources for clinicians and families; American College of Medical Genetics.

NM ACT Sheet for CPT I (CO/C16+C18) (ACMG) (PDF Document 123 KB)
Provides recommendations for clinical and laboratory follow-up of the newborn with out-of-range screening results, along with national and local resources for clinicians and families; American College of Medical Genetics.

Algorithm for Carnitine Palmitoyltransferase 1A (CPT 1) Deficiency [Elevated C0/C16+C18] (ACMG)
An algorithm of the basic steps involved in determining the final diagnosis of an infant with a positive newborn screen; American College of Medical Genetics.

Services for Patients & Families in New Mexico (NM)

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* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.

Helpful Articles

PubMed search for CPT1 deficiency, last 15 years.

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;142C(2):77-85. PubMed abstract / Full Text

Authors & Reviewers

Initial publication: March 2007; last update/revision: May 2023
Current Authors and Reviewers:
Author: Maggie Bale, MD, MPH
Senior Author: Brian J. Shayota, MD, MPH
Reviewer: Nancy C. Rose, MD
Authoring history
2022: update: Maggie Bale, MD, MPHA; Brian J. Shayota, MD, MPHSA; Kimberly Hart, MS, LCGCR
2012: revision: Kimberly Hart, MS, LCGCR
2007: first version: Nicola Longo, MD, Ph.D.A
AAuthor; CAContributing Author; SASenior Author; RReviewer

Page Bibliography

Bennet MJ, Santanii AB.
Carnitine Palmitoyltransferase 1A Deficiency.
GeneReviews; (2016) Accessed on Oct 28, 2022.

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;142C(2):77-85. PubMed abstract / Full Text

Schulze A, Lindner M, Kohlmuller D, Olgemoller K, Mayatepek E, Hoffmann GF.
Expanded newborn screening for inborn errors of metabolism by electrospray ionization-tandem mass spectrometry: results, outcome, and implications.
Pediatrics. 2003;111(6 Pt 1):1399-406. PubMed abstract