Carnitine palmitoyltransferase I deficiency is a rare

metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter the ...

that prevents the body from converting certain fats called long-chain

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

s(LCFA) into energy, particularly during periods without food. It is caused by a mutation in

CPT1A Carnitine palmitoyltransferase I (CPT1) also known as carnitine acyltransferase I, CPTI, CAT1, CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I, is a mitochondrial enzyme responsible for the formation of acyl carnitines by cat ...

chromosome 11 Chromosome 11 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome. Chromosome 11 spans about 135 million base pairs (the building material of DNA) and represents between 4 and 4.5 percent of the tot ...

Carnitine Carnitine is a quaternary ammonium compound involved in metabolism in most mammals, plants, and some bacteria. In support of energy metabolism, carnitine transports long-chain fatty acids into mitochondria to be oxidized for energy production, an ...

, 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 enzyme,

carnitine palmitoyltransferase I Carnitine palmitoyltransferase I (CPT1) also known as carnitine acyltransferase I, CPTI, CAT1, CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I, is a mitochondrial enzyme responsible for the formation of acyl carnitines by c ...

, that prevents these long-chain fatty acids from being transported into the

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

to be broken down.

Symptoms and signs

Signs and symptoms of this disorder include low levels of

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

s (hypoketosis) and low blood sugar (

hypoglycemia Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose belo ...

). Together these signs are called hypoketotic hypoglycemia. People with this disorder typically also have an enlarged

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

(

hepatomegaly Hepatomegaly is the condition of having an enlarged liver. It is a non-specific medical sign having many causes, which can broadly be broken down into infection, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdomi ...

), muscle weakness, and elevated levels of carnitine in the blood.

Genetics

Mutations in the ''

'' gene cause carnitine palmitoyltransferase I deficiency by producing a defective version of an enzyme called

. Without this enzyme, long-chain fatty acids from food and fats stored in the body cannot be transported into mitochondria to be broken down and processed. As a result, excessive levels of long-chain fatty acids may more rapidly build up in tissues, damaging the liver, heart and/or brain. This condition has an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

inheritance pattern, which means the defective gene must be inherited from both parents. The parents of a child with an autosomal recessive disorder are carriers of one copy of the defective gene, but are usually not affected by the disorder. The prevalence of mutations associated with this condition reach 68% to 81% in certain arctic coastal populations, suggesting that the condition had some adaptive value in those habitats at some time. Fewer than 50 people have been identified with this condition.

Diagnosis

Genetic testing is necessary for diagnosis.

Differential diagnosis

This condition is sometimes mistaken for fatty acid and ketogenesis disorders such as

Medium-chain acyl-coenzyme A dehydrogenase deficiency Medium-chain acyl-CoA dehydrogenase deficiency (MCAD deficiency or MCADD) is a disorder of fatty acid oxidation that impairs the body's ability to break down medium-chain fatty acids into acetyl-CoA. The disorder is characterized by hypoglycemia ...

(MCAD), other long-chain fatty acid oxidation disorders such as

Carnitine palmitoyltransferase II deficiency Carnitine palmitoyltransferase II deficiency is an autosomal recessively inherited genetic metabolic disorder characterized by an enzymatic defect that prevents long-chain fatty acids from being transported into the mitochondria for utilization ...

(CPT-II) and

Reye syndrome Reye syndrome is a rapidly worsening brain disease. Symptoms of Reye syndrome may include vomiting, personality changes, confusion, seizures, and loss of consciousness. While liver toxicity typically occurs in the syndrome, jaundice usually do ...

Treatment

Treatment for this condition is supportive. There is no cure. Affected people should eat a high-carbohydrate, low-fat diet and avoid fasting.

References

External links

''This article incorporates public domain text fro
The U.S. National Library of Medicine
' {{Medicine Autosomal recessive disorders Rare diseases Hepatology Fatty-acid metabolism disorders