NORD gratefully acknowledges Hannah K. Davis, MMSc, NORD Editorial Intern from the Emory University Genetic Counseling Training Program and Cecelia A. Bellcross, PhD, MS, CGC, Associate Professor, Director, Genetic Counseling Training Program, Emory University School of Medicine, for assistance in the preparation of this report.
Carnitine palmitoyltransferase 1A (CPT1A) deficiency is a disorder of fatty acid oxidation, the process by which the body breaks down fatty acids from food for energy. Fatty acids come from animal and vegetable fats. People with CPT1A deficiency may experience liver failure which can cause damage to the nervous system (hepatic encephalopathy) as a result of fatty acids not being properly broken down. CPT1A deficiency is caused by harmful DNA changes (mutations) in the CPT1A gene. The CPT1A gene produces the carnitine palmitoyltransferase 1 enzyme, which breaks down long fatty acids. CPT1A deficiency is an autosomal recessive condition, which means that a harmful change in the CPT1A gene was inherited from both parents.
CPT1A deficiency in a developing baby can cause abnormal findings during pregnancy, including maternal fatty liver, low blood sugar (hypoglycemia), abnormal liver enzymes, high amounts of ammonia (hyperammonenmia), and increased susceptibility to bleeding due to abnormal liver function.
CPT1A deficiency can be identified on newborn screening, a blood test performed on newborns shortly after birth. Newborn screening can detect levels of fatty acid oxidation products, and abnormal levels can indicate that a newborn has CPT1A deficiency. However, newborn screening is not diagnostic, and further testing is needed to confirm a diagnosis.
CPT1A deficiency symptoms typically appear after times of stress, like fasting or illness. These symptoms include low blood glucose and no ketone bodies in urine (hypoketotic hypoglycemia). Ketone bodies are molecules that are produced by the liver after fatty acids are broken down. Additionally, CPT1A deficiency can cause sudden liver failure. Liver failure can lead to damage to the nervous system (hepatic encephalopathy). Additionally, there can be other abnormal laboratory findings which may include increased liver enzymes, ammonia (hyperammonemia), and carnitine in blood.
CPT1A deficiency is caused by harmful changes (mutations) in the CPT1A gene that codes for the carnitine palmitoyltransferase 1 enzyme. This enzyme breaks down long fatty acids. If fats cannot be properly processed, then energy production is decreased.
CPT1A deficiency is an autosomal recessive condition. Autosomal recessive conditions occur when both parents carry a mutation on the same gene (carrier) and each parent passes the mutated gene on to the child, giving the child no normally functioning gene to compensate for the mutations.
If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the mutation and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive working genes from both parents and to not carry mutations from either parent that particular trait is 25%. The risk is the same for males and females.
CPT1A deficiency has been reported in approximately 60 individuals. The incidence of this condition may be higher in the Hutterite populations in the northern United States and Canada and the Inuit populations in northern Canada, Alaska and Greenland. This condition occurs in both males and females equally.
CPT1A deficiency can be diagnosed by using genetic testing to find two mutations in the CPT1A gene. Additionally, the level of carnitine palmitoyltransferase 1 (CPT1) enzyme can be measured from skin cells. Other laboratory findings can support this diagnosis, including low levels of ketones, elevated liver enzymes, elevated ammonia, and elevated carnitine in blood. Some state newborn screening programs perform screening for CPT1A deficiency by measuring the ratio of free to total carnitine in blood plasma or serum.
Without proper treatment and management, people with CPT1A deficiency can have severe hypoglycemia. Prevention of hypoglycemia is recommended to reduce the risk of neurological effects, such as seizures, unconsciousness, brain damage, and death. Hypoglycemia can be prevented with a high carbohydrate, low fat diet and frequent feeding. If acute hypoglycemia occurs, intravenous dextrose should be provided. Individuals with CPT1A deficiency should have regular liver function testing performed. Female carriers of an abnormal CPT1A gene should be informed about the possibility of complications if they become pregnant.
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