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. 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 enzyme that prevents these fats from being processed in the mitochondria.

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Types

There are three main types of carnitine palmitoyltransferase II deficiency:

• a lethal neonatal form
• a severe infantile hepatocardiomuscular form,
• a myopathic form

Neonatal 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.

Hepatocardiomuscular type

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.

Myopathic form

The myopathic form is the most frequently seen and least severe form of carnitine palmitoyltransferase II deficiency. It has a variable age of onset and is characterized 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.

Causes

Mutations in the CPT2 gene cause carnitine palmitoyltransferase II deficiency, leading to the production of a defective version of an enzyme called carnitine palmitoyltransferase II.

Without this enzyme, long-chain fatty acids from food and fats stored in the body cannot be broken down and processed.

Excessive levels of long-chain fatty acids may build up in tissues, damaging the heart, liver, and muscles and causing more serious complications.

This condition is inherited in an autosomal recessive pattern.

See also

• Primary carnitine deficiency
• Carnitine palmitoyltransferase I deficiency

This article incorporates public domain text from The U.S. National Library of Medicine