Carnitine Palmitoyltransferase II Deficiency

What is carnitine palmitoyltransferase II deficiency?

Carnitine palmitoyltransferase II 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 required by cells to process fats and produce energy. People with this disorder have a faulty enzyme that disrupts carnitine's role in processing long-chain fatty acids.

There are three main types of carnitine palmitoyltransferase II deficiency: a lethal neonatal form, a severe infantile hepatocardiomuscular form, and a myopathic form. Infants with the lethal neonatal form of this disorder usually experience respiratory failure, liver failure, seizures, and an irregular heart beat leading to cardiac arrest. In many cases, patients have malformed features and an abnormally developed brain and kidneys.

Signs and symptoms of the infantile hepatocardiomuscular type usually appear between 6 and 24 months of age. This condition involves recurring attacks of abnormally low levels of fat breakdown products and blood sugar (hypoketotic hypoglycemia) causing a loss of consciousness and seizures. Liver failure and an enlarged liver (hepatomegaly) are also sometimes seen. In many cases, there is also heart involvement. Episodes are often triggered by infections, fever, or fasting.

The myopathic form is the most frequently seen and is typically the least severe form of carnitine palmitoyltransferase II deficiency. It has a variable age of onset and is characterised by muscle pain (myalgia) and weakness. This condition is sometimes associated with the abnormal breakdown of an oxygen-binding muscle protein called myoglobin (myoglobinuria). Myoglobinuria can cause kidney failure and death.

How common is carnitine palmitoyltransferase II deficiency?

The lethal neonatal form of this disorder has been described in more than 10 families, while the severe infantile hepatocardiomuscular form has been identified in approximately 20 families. More than 200 cases of the myopathic form have been identified.

What genes are related to carnitine palmitoyltransferase II deficiency?

Mutations in the CPT2 gene cause carnitine palmitoyltransferase II deficiency.

Mutations in the CPT2 gene lead to the production of a defective version of an enzyme called carnitine palmitoyltransferase II. Together with carnitine, this enzyme helps transport long-chain fatty acids into the inner compartment of mitochondria, the energy-producing centers within cells. If this enzyme is defective, long-chain fatty acids from food and fats stored in the body cannot be 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 myalgia, weakness, and hypoglycemia. Excessive levels of long-chain fatty acids may build up in tissues, damaging the heart, liver, and muscles and causing more serious complications.

How do people inherit carnitine palmitoyltransferase II deficiency?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

What other names do people use for carnitine palmitoyltransferase II deficiency?

  • CPT2 - Carnitine palmitoyltransferase II deficiency
  • CPTII - Carnitine palmitoyltransferase deficiency type II
  • Muscle form of carnitine palmitoyltransferase deficiency

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