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. In people with primary carnitine deficiency, proteins called carnitine transporters do not work properly. These proteins normally bring carnitine into cells and prevent the escape of carnitine from the body in urine.

Typically, initial signs and symptoms of this disorder occur during infancy or early childhood and often include changes in brain tissue (encephalopathy) resulting in functional abnormalities; 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. Severe 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.

The incidence of primary carnitine deficiency in the general population is approximately 1 in 100,000 newborns. In Japan, this disorder affects 1 in every 40,000 newborns.

Mutations in the SLC22A5 gene cause primary carnitine deficiency.

Mutations in the SLC22A5 gene lead to the production of defective carnitine transporters. As a result of reduced transport of carnitine into cells, cells are not supplied with an adequate amount of this substance and it is lost from the body in urine. Without carnitine, fats cannot be processed correctly and are not converted into energy, which can lead to characteristic signs and symptoms of this disorder.

Read more about the SLC22A5 gene.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the mutated gene. Carriers of SLC22A5 mutations may have some signs and symptoms related to the condition.