Carnitine Uptake Defect

Other Names


Carnitine uptake deficiency

Carnitine transporter deficiency

Systemic carnitine deficiency (SCD)

Primary carnitine deficiency

Diagnosis Coding

E71.41, primary carnitine deficiency

Disorder Category

A fatty acid oxidation disorder



Decreased C0 and other acylcarnitines (C3, C16, C18)

Tested By

Tandem mass spectrometry (MS/MS); sensitivity=100% (80% with the first screen only [Nicola Longo, personal communication 2006]); specificity=99.97% [Schulze: 2003]


Carnitine uptake deficieny (CUD) results in urinary carnitine wasting and systemic and intracellular carnitine deficiency. The latter results in an intramitochondrial defect in the beta-oxidation of fatty acids that impairs energy production and causes accumulation of free fatty acids. The increased reliance on fat metabolism for energy production during prolonged fasting and/or periods of increased energy demands (fever, stress, lack of sleep) may cause metabolic crises in patients with carnitine deficiency. Mutations in the SLC22A5 gene cause CUD. This gene is responsible for making a protein called OCTN2 that transports carnitine into cells.


Approximately 1 in 40,000 [Koizumi: 1999], with about 1% of the normal US population being heterozygous (carriers) for this condition [Amat: 2008]


Autosomal recessive

Prenatal Testing

DNA testing possible by amniocentesis or chorionic villus sampling (CVS) if both disease causing mutations of an affected family member have been identified. Gunctional assay (carnitine transport) possible by amniocentesis or CVS.

Other Testing

Genetic testing is possible for at-risk family members if both disease causing mutations of an affected family member have been identified.

Clinical Characteristics

With treatment prior to metabolic crises, outcomes should be normal. Treatment may reverse pre-existing cardiomyopathy and muscle weakness, but not developmental delay. Without treatment, symptoms may begin between birth and three years of age or, in the myopathic form, symptoms usually begin before seven years and may not include metabolic crisis episodes or hypoglycemia. Some children remain asymptomatic for life. Patients are at risk of sudden death from arrhythmia at any age.

Inital signs and symptoms may include:
  • poor appetite
  • vomiting
  • irritability
  • lethargy
  • hypoketotic hypoglycemia
  • sudden death
  • lab findings:
    • anemia
    • metabolic acidosis
    • hypoglycemia

Subsequent finding include:
  • muscle weakness
  • cardiomyopathy
  • cardiac arrhythmia
  • hepatomegaly
  • seizures and
  • brain injury from hypoglycemia

Treatment consists of carnitine supplementation. Mothers with primary carnitine deficiency can be identified by newborn screening of their unaffected infant.[Schimmenti: 2007]

Follow-up Testing after Positive Screen

Plasma and urine carnitine analysis (the latter to measure urinary carnitine reabsorption), carnitine transporter functional analysis in fibroblasts and/or SLC22A5 gene sequencing.

Primary Care Management

Upon Notification of the + Screen

If the Diagnosis is Confirmed

  • Educate the family regarding signs, symptoms, and the need for urgent care when the infant becomes ill (see Carnitine Uptake Deficiency - Information for Parents (STAR-G)).
  • Special diet is not required but frequent feedings and avoidance of fasting is important.
  • Oral L-carnitine supplements should be continued for life.
  • For those identified after irreversible consequences, assist in management, particularly with developmental and educational interventions.

Specialty Care Collaboration

Initial consultation and ongoing collaboration if the child is affected. A dietician may work with the family to devise an optimal approach to dietary management. Genetic counseling for the family.


Information & Support

For Professionals

ACT Sheet for Carnitine Uptake Defect (ACMG) (PDF Document 344 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical Genetics.

Newborn Screening ACT Sheets & Confirmatory Algorithms (ACMG)
ACTion (ACT) Sheets and algorithms for responding to positive newborn screening test results, membership required; American College of Medical Genetics.

Resources for Carnitine Uptake Deficiency (Disease InfoSearch)
Compilation of information, articles, research, case studies, and genetics links; from Genetic Alliance.

Carnitine Uptake Deficiency (OMIM)
Information about clinical features, diagnosis, management, and molecular and population genetics; Online Mendelian Inheritance in Man, authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine

Genetics in Primary Care Institute (AAP)
Contains health supervision guidelines and other useful resources for the care of children with genetic disorders; American Academy of Pediatrics.

Genetics in Primary Care Institute (AAP)
Contains health supervision guidelines and other useful resources for the care of children with genetic disorders; American Academy of Pediatrics.

For Parents and Patients

Carnitine Uptake 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.

Carnitine Uptake Deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

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

Services for Patients & Families in Montana (MT)

Genetics clinic services throughout the US can be found through the Genetics Clinic Services Search Engine (ACMG).
Genetics clinic services throughout the US can be found through the Genetics Clinic Services Search Engine (ACMG).

For services not listed above, browse our Services categories or search our database.

* 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.

Authors & Reviewers

Initial publication: March 2007; last update/revision: June 2012
Current Authors and Reviewers:
Author: Nicola Longo, MD, Ph.D.
Reviewer: Kimberly Hart, MS, LCGC

Page Bibliography

Amat di San Filippo C, Taylor MR, Mestroni L, Botto LD, Longo N.
Cardiomyopathy and carnitine deficiency.
Mol Genet Metab.. 2008;94(2):162-166.
Carnitine is essential for the transfer of long-chain fatty acids across the mitochondrial membrane for subsequent beta-oxidation. Study results indicate heterozygosity for primary carnitine deficiency is not more frequent in patients with unselected types of cardiomyopathy and is unlikely to be an important cause of cardiomyopathy in humans.

Koizumi A, Nozaki J, Ohura T, Kayo T, Wada Y, Nezu J, Ohashi R, Tamai I, Shoji Y, Takada G, Kibira S, Matsuishi T, Tsuji A.
Genetic epidemiology of the carnitine transporter OCTN2 gene in a Japanese population and phenotypic characterization in Japanese pedigrees with primary systemic carnitine deficiency.
Hum Mol Genet. 1999;8(12):2247-54. PubMed abstract

Schimmenti LA, Crombez EA, Schwahn BC, Heese BA, Wood TC, Schroer RJ, Bentler K, Cederbaum S, Sarafoglou K, McCann M, Rinaldo P, Matern D, di San Filippo CA, Pasquali M, Berry SA, Longo N.
Expanded newborn screening identifies maternal primary carnitine deficiency.
Mol Genet Metab. 2007;90(4):441-5. PubMed abstract
Primary carnitine deficiency impairs fatty acid oxidation and can result in hypoglycemia, hepatic encephalopathy, cardiomyopathy and sudden death. Given the lifetime risk of morbidity or sudden death, identification of adult patients with primary carnitine deficiency is an added benefit of expanded newborn screening programs.

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