What is primary carnitine deficiency?

Primary carnitine deficiency is a condition that prevents the body from using fats for energy, particularly during periods without food (fasting). Carnitine, a natural substance acquired mostly through diet, is used by cells to process fats and produce energy. People with primary carnitine deficiency have defective proteins called carnitine transporters, which bring carnitine into cells and prevent its escape from the body.

What are the symptoms of primary carnitine deficiency?
Typically, initial signs and symptoms of this disorder occur during infancy or early childhood and often include brain function abnormalities (encephalopathy); an enlarged, poorly pumping heart (cardiomyopathy); confusion; vomiting; muscle weakness; and low blood sugar (hypoglycemia). Serious complications such as heart failure, liver problems, coma, and sudden unexpected death are also a risk. Acute illness due to primary carnitine deficiency can be triggered by periods of fasting or illnesses such as viral infections, particularly when eating is reduced.

This condition is sometimes mistaken for Reye syndrome, a severe disorder that develops 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. Primary carnitine deficiency progresses very slowly.

How is it diagnosed?

Several specialized tests may used to confirm a suspected diagnosis:

Blood tests can be used to detect the presence of certain chemicals in the blood that may indicate some metabolic diseases.

An exercise test is used to monitor a person’s response to intense or moderate exercise. Blood samples are taken during exercise for testing.

Electromyography (EMG) uses small needle electrodes to measure the electrical currents in a muscle as it contracts. While an EMG can’t definitively diagnose metabolic disease, it can be used to rule out a number of other types of neuromuscular disease that cause similar patterns of weakness.

A muscle biopsy requires the removal of a small piece of muscle tissue for microscopic analysis. The procedure is done either surgically, with an incision to expose the target muscle, or with a needle. A skin biopsy is also sometimes performed.

Other tests that may be needed include an electrocardiogram to test heart function, and brain imaging studies such as CT or MRI scans.

Genetic tests, using a blood sample, can analyze the person’s genes for particular defects that cause metabolic disease, but these tests often aren’t necessary for diagnosis or for determining treatment.

How common is primary carnitine deficiency?

Primary carnitine deficiency affects 1 in every 40,000 live births in Japan and 1 in every 37,000 to 100,000 newborns in Australia. The incidence of this condition in other populations is unknown, but is probably similar to that reported for Japan.

What genes are related to primary carnitine deficiency?

Primary carnitine deficiency is caused by a change (also known as a mutation) in the gene called the SLC22A5 gene.
Mutations in the SLC22A5 gene lead to the production of defective carnitine transporters. As a result of reduced transport function, carnitine is lost from the body and cells are not supplied with an adequate amount of carnitine. Without carnitine, fats cannot be processed correctly and are not converted into energy, which can lead to characteristic signs and symptoms of this disorder.

How do people inherit primary carnitine deficiency?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene. Carriers may have some signs and symptoms related to the condition.

What other names do people use for primary carnitine deficiency?

  • Carnitine transporter deficiency
  • carnitine uptake defect
  • carnitine uptake deficien
  • CUD
  • Renal carnitine transport defect
  • Systemic carnitine deficiency

Is there any treatment for primary carnitine deficiency?

Primary carnitine deficiency can often be treated successfully with carnitine supplements.