Fatty-acid oxidation disorder

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 31, 2016
StartDiseasesFatty-acid oxidation disorder

Fatty-acid oxidation defects (FAOD) or fatty-acid oxidation disorders are inborn errors of metabolism, which are rare genetic disorders affecting metabolism. Newborn screening will test for these defects which usually present in infancy, though they can present in adulthood as well. Detecting the conditions early can help a parent provide a healthy life for a child. However, when this condition goes undiagnosed and untreated, it can lead to significant health risks and even death.


Definition & Facts

A baby born with a fatty acid oxidation defect does not have the capability to break down fatty acids. The body naturally uses glucose to supply the energy the body needs. When the body depletes glucose, it turns to the fatty acids for energy. A process called oxidation breaks down fatty acids to give energy. Different enzymes in the system are responsible for the oxidation process.

A body that is unable to carry out this process will have trouble maintaining proper glucose levels, and there will be a buildup of fatty acids in the system. Both males and females can suffer from these defects. The type of disorder depends on the enzyme that is missing.

Types of fatty-acid oxidation disorders include long-chain hydroxyacyl-CoA dehydrogenase deficiency, carnitine uptake defect, medium-chain acyl-CoA dehydrogenase deficiency, trifunctional protein deficiency, and very-long-chain acyl-CoA dehydrogenase deficiency.

Symptoms & Complaints

It is extremely rare for symptoms of FAOD to appear in adults. The signs that manifest themselves in babies and young children depend on the type of disorder. Symptoms can also differ from one child to the next with the same disorder.

FAOD can be asymptomatic unless certain conditions are present, one of which is fasting. When there is no excessive demand for energy and the patient is feeding well, then it is hard for symptoms to show. In infants and young children, oxidation of fatty acids occurs 12 hours after fasting and 16-24 hours for older children. Some of the signs include:

Failure to get treatment promptly can lead to health conditions such as:


When fats break down in the body, they leave residues called fatty acids. Human bodies store these fatty acids for later use when there is a need for energy, and the primary source is not available. Genetic mutations in some proteins prevent them from carrying out the oxidation process. These defects are passed down from the parent in an autosomal recessive pattern.

Diagnosis & Tests

A patient's medical history and family history will be inquired about. Both blood tests and clinical urine tests will be used to analyze acylcarnitine levels as well as carnitine levels. Acylcarnitines are compounds in humans and other living organisms that facilitate the breakdown of fatty acids. It is preferable to run many types of tests within 24 hours after birth.

Treatment & Therapy

The treatment of a fatty acid oxidation defect involves maintenance of proper blood sugar levels. Children with an oxidation deficiency should avoid fasting at all times. During an ailment, a child may require intensive medical management to avoid aggravating the condition.

Providing a proper diet is an important component of managing FAOD. A low-fat diet and carbohydrate-rich diet is highly recommended.

In severe cases, a child may need drugs such as carnitine, bezafibrate, or riboflavin. Dextrose can also be administered to prevent hypoglycemia. The type of disorder will determine the treatment approaches that a doctor prescribes. A metabolic specialist can create a medical plan specific to the patient and disorder. 

Prevention & Prophylaxis

Whether a child is born with a fatty acid oxidation disorder is a matter of genetics. The safest bet is to conduct screening for early diagnosis so that treatment and management can start early.

Genetic testing may be suitable for prospective parents who have other children with a defect. Families affected by FAOD should obtain accurate information and support regarding care.