Carnitine-acylcarnitine translocase deficiency

Carnitine-acylcarnitine translocase deficiency is a condition that prevents the body from converting certain fats called long-chain fatty acids into energy, particularly during periods without food (fasting). Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. People with this disorder have a faulty transporter that disrupts carnitine's role in processing long-chain fatty acids.

The signs of carnitine-acylcarnitine translocase deficiency usually begin within the first few hours after birth. Seizures, an irregular heartbeat (arrhythmia), and breathing problems are often the first signs of this disorder. This disorder may also result in an extremely low level of ketones, which are products of fat breakdown that are used for energy. Low blood sugar (hypoglycemia) is another major feature. Together these signs are called hypoketotic hypoglycemia, which can result in unconsciousness and seizures. Other signs that are often present include excess ammonia in the blood (hyperammonemia), an enlarged liver (hepatomegaly), heart abnormalities (cardiomyopathy), and muscle weakness. This disorder can cause sudden infant death.

This condition is very rare; approximately 30 cases have been confirmed.

Mutations in the SLC25A20 gene cause carnitine-acylcarnitine translocase deficiency.

Mutations in the SLC25A20 gene lead to the production of a defective version of a transporter called carnitine-acylcarnitine translocase. A shortage of functional transporters prevents long-chain fatty acids from food and fats stored in the body from being broken down and processed. As a result, these fatty acids are not converted into energy, which can lead to characteristic signs and symptoms of this disorder, such as weakness, hypoglycemia, and an irregular heartbeat. Excess long-chain fatty acids, with or without carnitine attached to them, can affect the electrical properties of heart (cardiac) cells. This abnormal accumulation of fatty acids can cause heart damage and an irregular heart beat that can lead to cardiac arrest. Fatty acids may also build up in other tissues and can damage the liver and muscles, resulting in serious, sometimes life-threatening, complications.

Read more about the SLC25A20 gene.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.