Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency is a rare autosomal recessive fatty acid oxidation disorder[1] that prevents the body from converting certain fats into energy.

[citation needed] Typically, initial signs and symptoms of this disorder occur during infancy or early childhood and can include feeding difficulties, lethargy, hypoglycemia, hypotonia, liver problems, and abnormalities in the retina.

Long-chain fatty acids from food and body fat cannot be metabolized and processed 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.

Prior to widespread inclusion of FAO (fatty acid oxidation) disorders in newborn screening tests, diagnosis typically occurred as a result of children presenting for medical attention having hypoglycemic hypoketotic crisis.