3-hydroxyacyl-coenzyme A dehydrogenase deficiency is a rare condition that prevents the body from converting certain fats to energy, particularly during fasting. Normally, through a process called

fatty acid oxidation Fatty is a derogatory term for someone who is obese. It may refer also to: People * Mai Fatty, Gambian politician * Roscoe Arbuckle (1887–1933), American actor and comedian * Fatty Briody (1858–1903), American Major League Baseball player ...

, several enzymes work in a step-wise fashion to metabolize fats and convert them to energy. People with 3-hydroxyacyl-coenzyme A dehydrogenase deficiency have inadequate levels of an enzyme required for a step that metabolizes groups of fats called

medium chain fatty acid Medium-chain triglycerides (MCTs) are triglycerides with two or three fatty acids having an aliphatic tail of 6–12 carbon atoms, i.e. medium-chain fatty acids (MCFAs). Rich food sources for commercial extraction of MCTs include palm kernel oil a ...

s and

short chain fatty acid Short-chain fatty acids (SCFAs) are fatty acids with fewer than six carbon atoms. Derived from intestinal microbial fermentation of indigestible foods, SCFAs are the main energy source of colonocytes, making them crucial to gastrointestinal health ...

s; for this reason this disorder is sometimes called medium- and short-chain 3-hydroxyacyl-coenzyme A dehydrogenase (M/SCHAD) deficiency.

Signs and symptoms

Typically, initial signs and symptoms of this disorder occur during infancy or early childhood and can include poor appetite, vomiting, diarrhea,

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

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 bel ...

hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases ...

, liver problems, and

hyperinsulinism Hyperinsulinism refers to an above normal level of insulin in the blood of a person or animal. Normal insulin secretion and blood levels are closely related to the level of glucose in the blood, so that a given level of insulin can be normal for o ...

(high levels of insulin). Insulin controls the amount of sugar that moves from the blood into cells for conversion to energy. Individuals with 3-hydroxyacyl-coenzyme A dehydrogenase deficiency are also at risk for complications such as seizures, life-threatening heart and breathing problems, coma, and sudden unexpected death. Problems related to 3-hydroxyacyl-coenzyme A dehydrogenase deficiency can be triggered by periods of fasting or by illnesses such as viral infections. This disorder is sometimes mistaken for

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 usuall ...

, a severe disorder that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome are associated with the use of aspirin during these viral infections.

Genetics

Mutations in the ''HADH'' gene lead to inadequate levels of an enzyme called

3-hydroxyacyl-coenzyme A dehydrogenase In enzymology, a 3-hydroxyacyl-CoA dehydrogenase () is an enzyme that catalyzes the chemical reaction :(S)-3-hydroxyacyl-CoA + NAD+ \rightleftharpoons 3-oxoacyl-CoA + NADH + H+ Thus, the two substrates of this enzyme are (S)-3-hydroxyacyl- ...

. Medium-chain and short-chain fatty acids cannot be metabolized and processed properly without sufficient levels of this enzyme. As a result, these fatty acids are not converted to energy, which can lead to characteristic features of this disorder, such as lethargy and hypoglycemia. Medium-chain and short-chain fatty acids or partially metabolized fatty acids may build up in tissues and damage the liver, heart, and muscles, causing more serious complications. 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 each carry one copy of the altered gene but do not show signs and symptoms of the disorder.

Signs and symptoms

Genetics

Diagnosis

Treatment

See also

References

External links