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Genetic and Rare Diseases Information Center (GARD)

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Primary carnitine deficiency

Other Names for this Disease
  • Carnitine deficiency, systemic, due to defect in renal reabsorption of carnitine
  • Carnitine plasma-membrane transporter deficiency
  • Carnitine transporter deficiency
  • Carnitine uptake defect
  • Carnitine uptake deficiency
More Names
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Your Question

What is this? Why do I have it? I just had a baby and found out I had it. My sister also just had a baby and has it too. Will we be okay?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is primary carnitine deficiency?

Primary carnitine deficiency is a genetic condition that prevents the body from using certain fats for energy, particularly during periods without food (fasting). The nature and severity of signs and symptoms may vary, but they most often appear during infancy or early childhood and can include severe brain dysfunction (encephalopathy), cardiomyopathy, confusion, vomiting, muscle weakness, and hypoglycemia.[1] Some individuals may only have fatigability in adulthood, or no symptoms at all. This condition is caused by mutations in the SLC22A5 gene and is inherited in an autosomal recessive manner. Treatment and prevention of symptoms typically includes oral L-carnitine supplementation.[2]
Last updated: 7/9/2012

What causes primary carnitine deficiency?

Mutations in the SLC22A5 gene cause primary carnitine deficiency. This gene provides instructions for making a protein called OCTN2 that transports carnitine into cells. Cells need carnitine to bring certain types of fats (fatty acids) into mitochondria, which are the energy-producing centers within cells. Fatty acids are a major source of energy for the heart and muscles. During periods of fasting, fatty acids are also an important energy source for the liver and other tissues.

Mutations in the SLC22A5 gene result in an absent or dysfunctional OCTN2 protein. As a result, there is a shortage (deficiency) of carnitine within cells. This deficiency, as well as potential build-up of fatty acids within the cells, causes the signs and symptoms of the condition.[3]
Last updated: 7/9/2012

How is primary carnitine deficiency inherited?

Primary carnitine deficiency is inherited in an autosomal recessive manner. Individuals have two copies of each gene, one of which is inherited from each parent. For an individual to have an autosomal recessive condition, he/she must have a mutation in both copies of the disease-causing gene. The parents of an affected individual, who each likely have one mutated copy, are referred to as carriers. Carriers typically do not have any signs or symptoms of the condition. When two carriers for an autosomal recessive condition have children together, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% risk to not have the condition and not be a carrier.
Last updated: 7/9/2012

When might individuals with primary carnitine deficiency be diagnosed?

Primary carnitine deficiency can have a wide range of presentations and the age at diagnosis varies. Affected individuals may be diagnosed due to metabolic decompensation in infancy (between ages 3 months to 2 years); cardiomyopathy in childhood (between 2 and 4 years of age on average); or fatigability in adulthood. Some affected individuals lack symptoms entirely.[4]

Although the condition is typically associated with the infantile presentation in about half of affected individuals and the childhood myopathic presentation in the other half, affected adults with mild or no symptoms have been reported. Several women have been diagnosed after newborn screening identified low carnitine levels in their infants. About half of those women complained of fatigability, whereas the other half were asymptomatic. In some cases, affected women can have decreased stamina or worsening of cardiac arrhythmia during pregnancy, suggesting that the condition may manifest or exacerbate during pregnancy.[4]
Last updated: 7/11/2012

What is the prognosis for primary carnitine deficiency?

Infantile metabolic and childhood myopathic presentations of the condition can be fatal if untreated.[4] However, long-term prognosis is excellent with oral carnitine supplementation. If the disorder goes unrecognized, death can occur due to cardiac failure, arrhythmias or sudden death. Hypoglycemia or sudden deaths from arrhythmias (even without cardiomyopathy) have been reported in affected individuals who stop their carnitine supplementation against medical advice.[5]

Individuals who have questions about their specific prognosis should speak with their health care provider.
Last updated: 7/11/2012