Primary carnitine deficiency is a genetic disorder in which the body is unable to metabolise fatty acids due to dysfunction or deficiency of carnitine transporter. The disease may be triggered by periods of fasting or viral infections when the energy demand of the body is very high. Carnitine transporters are proteins that play a critical role in maintaining optimal levels of carnitine, which is essential for energy production through effective transportation of fatty acids into mitochondrial matrix. The signs and symptoms associated with primary carnitine deficiency are encephalopathy, cardiomyopathy, confusion, vomiting, myopathy, and hypoglycemia. In acute cases, complications such as heart failure, liver problems, coma, and sudden unexpected death can occur.

Homozygous or compound heterozygous mutation in the SLC22A5 gene (Solute Carrier Family 22 Member 5) is associated with primary carnitine deficiency.