Carnitine-acylcarnitine translocase deficiency is a rare,

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 ...

metabolic disorder that prevents the body from converting long-chain fatty acids into energy, particularly during periods without food.

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 that prevents long-chain fatty acids from being transported into the innermost part of 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 ...

for processing.

Presentation

The signs of carnitine-acylcarnitine translocase deficiency usually begin within the first few hours of life. Seizures, an irregular

heartbeat A heartbeat is one cardiac cycle of the heart. Heartbeat, heart beat, heartbeats, and heart beats may refer to: Computing *Heartbeat (computing), a periodic signal to indicate normal operation or to synchronize parts of a system *Heartbeat, clus ...

, and breathing problems are often the first signs of this disorder. This disorder may also cause extremely 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 (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 Cardiomyopathy is a group of diseases that affect the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. A ...

), and muscle weakness. This disorder can cause

sudden infant death Sudden infant death syndrome (SIDS) is the sudden unexplained death of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough autopsy and detailed death scene investigation. SIDS usual ...

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. Free long-chain fatty acids or those that are joined with carnitine can affect the electrical properties of cardiac cells causing an irregular heart beat (

arrhythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...

, which can lead to cardiac arrest). Fatty acids may also build up in tissues and can damage the heart, liver, and muscles, and cause more serious complications. This condition has an

inheritance pattern, which means the defective gene is located on an

autosome An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...

, and two copies of the gene - one from each parent - must be inherited to be affected by the disorder. 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.

Diagnosis

Treatment

References

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The U.S. National Library of Medicine
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