Primary carnitine deficiency is a condition where the body can’t properly turn fats into energy. This happens because of a problem with the protein that carries carnitine, a natural substance from an amino acid. If not found and treated early, it can hurt the brain and be very dangerous.
Without treatment, primary carnitine deficiency weakens the heart muscles, making it harder to pump blood, and makes the heart larger (cardiomyopathy). The liver might also get bigger. This condition can also make muscles weak and cause very low blood sugar (hypoglycemia), which can hurt the brain. Even though this brain damage might lead to lasting learning problems or disability, the other symptoms usually go away when a person starts taking L-carnitine supplements. Without these supplements, someone with primary carnitine deficiency is at risk for a “metabolic crisis” (like feeling tired, cranky, having a fever, feeling sick, or having low blood sugar) if they go a long time without eating (fasting) or if they’re sick. If not treated, this crisis can cause seizures, brain swelling, and other very serious problems. People with primary carnitine deficiency will need to take L-carnitine supplements for their whole lives. If kids start having heart or muscle problems, taking L-carnitine can usually help. A healthcare provider might also suggest that people with primary carnitine deficiency eat more often, especially when they’re young or sick.
Primary carnitine deficiency is caused by pathogenic (disease-causing) variants in the SLC22A5gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.
Carriers of primary carnitine deficiency do not typically show symptoms of the disease. However, there may be an increased risk of serious pregnancy complications, particularly in the third trimester, in women carrying a fetus affected with this disorder.
Other names for this condition are carnitine transporter deficiency, carnitine uptake defect, renal carnitine transport defect, and systemic carnitine deficiency
Resources:
Revised November 2023
