Carnitine palmitoyltransferase I deficiency
Carnitine palmitoyltransferase I (CPT I) deficiency is a metabolic disorder that prevents the body from using certain fats for energy, particularly during periods of fasting or illness.
Overview
CPT I deficiency is a fatty acid oxidation disorder. It prevents the body from breaking down long-chain fatty acids into energy. This is particularly problematic during fasting, when the body relies on fat stores for fuel.
Symptoms
Symptoms are often triggered by fasting or illness and include:
- Hypoketotic hypoglycemia: Low blood glucose and low levels of ketones, which can cause confusion, lethargy, or seizures.
- Hepatomegaly: An enlarged liver that may fail to remove toxins, leading to hepatic encephalopathy (impaired brain function).
The condition carries risks of nervous system damage, liver failure, coma, and sudden death. Some individuals may experience no symptoms at all, while others may face health crises from infancy through adulthood.
Causes
The condition is caused by variants in the CPT1A gene, which provides instructions for the enzyme carnitine palmitoyltransferase 1A. This enzyme is responsible for attaching carnitine to long-chain fatty acids, allowing them to enter the mitochondria to be converted into energy.
When this enzyme is deficient, fatty acids cannot enter the mitochondria. This leads to reduced energy production and the buildup of fatty acids and related compounds, which can damage the liver, heart, and brain.
Inheritance
This condition is inherited in an autosomal recessive pattern, meaning both copies of the gene must have a variant to cause the disorder. Carriers (parents with one variant) typically do not show symptoms. However, pregnant women who carry one CPT1A variant and are carrying a fetus with two variants are at risk for acute fatty liver of pregnancy (AFLP), a condition that can progress to liver failure.