Carnitine-acylcarnitine translocase deficiency is a rare, autosomal recessive metabolic disorder that prevents the body from converting 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 long-chain fatty acids from being transported into the innermost part of the mitochondria for processing. Presentation
The signs of carnitine-acylcarnitine translocase deficiency usually begin within the first few hours of life. Seizures, an irregular heartbeat, and breathing problems are often the first signs of this disorder. This disorder may also cause extremely low levels of ketones (products of fat breakdown that are used for energy) and low blood sugar (hypoglycemia). Together, these two signs are called hypoketotic hypoglycemia. Other signs that are often present include ammonia in the blood (hyperammonemia), an enlarged liver (hepatomegaly), heart abnormalities (cardiomyopathy), and muscle weakness. This disorder can cause sudden infant death. Pathophysiology
Mutations in the SLC25A20 gene lead to the production of a defective version of an enzyme called carnitine-acylcarnitine translocase. Without this enzyme, 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 weakness, hypoglycemia, and an irregular heartbeat.
The AHCY gene provides instructions for producing the enzyme S-adenosylhomocysteine hydrolase. This enzyme converts the S-adenosyl homocysteine into the compound homocysteine. Homocysteine may be converted back to methionine or into another amino acid, cysteine.A deficiency of any of these enzymes results in a buildup of methionine in the body, and may cause signs and symptoms related to hypermethioninemia. Diagnosis
People with hypermethioninemia often do not show any symptoms. Some individuals with hypermethioninemia exhibit learning disabilities, mental retardation, and other neurological problems; delays in motor skills such as standing or walking; sluggishness; muscle weakness; liver problems; unusual facial features; and their breath, sweat, or urine may have a smell resembling boiled cabbage.Hypermethioninemia can occur with other metabolic disorders, such as homocystinuria, tyrosinemia and galactosemia, which also involve the faulty breakdown of particular molecules. It can also result from liver disease or excessive dietary intake of methionine from consuming large amounts of protein or a methionine-enriched infant formula. Treatment
See also
List of amino acid metabolism disorders

References


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