Fatty Acid Oxidation Disorders (FAQ)

Answers to questions families often have about caring for their child with a fatty oxidation disorder, such as MCADD, LCHADD, or VLCADD

Fatty acid oxidation disorders are inherited genetic conditions. Children with a fatty acid oxidation disorder have an insufficient functioning enzyme activity needed to break down certain types of fat. This can cause problems because fats are needed to produce energy, and toxins can build up in the body when the process does not work as it should. A metabolic crisis happens when the body runs out of energy and cannot produce any more from stored fat. It can occur when a child has not eaten in a long time or when extra energy is needed, for example, to fight an infection, deal with stress, lack of sleep, or prolonged exercise. A metabolic crisis can present with a low blood sugar level, a build-up of toxins, and organ damage, most frequently involving the muscles and heart. Other problems that can happen include an abnormal heart rhythm, heart disease, muscle pain, and kidney damage. Babies get screened for these disorders right after birth. Among the many fatty acid oxidation disorders are MCADD (medium-chain acyl-CoA dehydrogenase deficiency), LCHADD (long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency), VLCADD (very long-chain acyl-CoA dehydrogenase deficiency), CPT1 (carnitine palmitoyltransferase I) deficiency, and CPT2 (carnitine palmitoyltransferase II) deficiency.

Fatty acid oxidation disorders are caused by inherited genetic mutations or changes in one of the genes that creates one of the enzymes needed to metabolize fats. The disorders are described as a recessive trait. This means that both parents are typically carriers with only 1 of their 2 copies of the gene mutated, but their diagnosed child has inherited both mutated copies and therefore does not have any normal copies of the gene. Notably, carriers do not experience any symptoms of the condition.

Children with these conditions may have no symptoms when they are healthy and eating well. Symptoms are often brought on by illness and fasting and may become more severe if treatment is not started early. Symptoms differ by the specific type of fatty acid oxidation disorder and by how severely they may be affected. Symptoms can start as early as the newborn period or as late as adulthood in more mild cases. Initial symptoms/signs may include:

• Poor feeding
• Vomiting
• Lethargy
• Hypotonia (low muscle tone)
• Hepatomegaly (enlarged liver)
• Cardiac insufficiency
• Abnormal lab findings: elevated liver and muscle enzymes, increased fatty acid levels, low blood sugar
• Rhabdomyolysis (breakdown of muscle tissue)

Any symptoms need to be monitored by a doctor and may require treatment in the emergency room. Without effective treatment, complications may include:

• Liver disease
• Heart disease
• Cardiac conduction defects
• Peripheral neuropathy
• Myopathy (muscle disease)
• Seizures
• Brain damage
• Death

These disorders are usually diagnosed by newborn screening. Analysis of acylcarnitines (checking for remnants of the fatty acid breakdown process) in blood and often genetic testing will be recommended to confirm the diagnosis. The newborn screening program will usually refer patients to a metabolic geneticist so that further testing can be performed. Importantly, an abnormal newborn screen alone does not confirm a diagnosis, which is why additional testing is necessary.

There is a wide spectrum of severity for all of these conditions. Generally speaking, though, children diagnosed with a fatty acid oxidation disorder can live fairly normal lives with normal growth and development, assuming that they receive proper treatment and adhere to precautionary measures. Lifelong management of the disorder is needed. Avoiding episodes of prolonged illness, fasting, and dehydration is vital for improving outcomes.

All of these disorders are recessive. If parents have a child with this condition, both parents are carriers of the abnormal gene, and therefore each pregnancy between the same 2 parents has a 1:4 chance of also being affected. Any prior children who are healthy and had a normal newborn screen do not need to be tested. Unaffected children in the family, as well as extended family members, may choose to be tested when they are adults to see if they are carriers. Talk to your doctor about any concerns you have regarding others in the family having the disorder, and ask questions about testing.

After diagnosis, the main goal of treatment is to avoid progression of the disease and acute problems (called a “crisis”) brought about by illness, fasting, or dehydration. Intravenous glucose, usually given in an emergency room, is necessary during illness as an energy source and to prevent dehydration. The metabolic geneticist, your child's medical home, and your family should have a treatment protocol, which is a written plan for acute illnesses. The treatment team often involves a dietitian or nutritionist for those that require dietary interventions, which will be determined by the metabolic geneticist. This may include a heart-healthy diet with limitations on fat intake, which may require the use of specialized medical formulas. Some doctors may prescribe levocarnitine (L-carnitine) if found to have a secondary deficiency.

Your family will need to follow strict guidelines on nutrition, illness, and fasting limitations. Your child may need medications, depending on the enzyme deficiency, and specialized medical formulas. (See Formulas for Metabolic Conditions ( 138 KB).) Support groups may be helpful. Because these are rare disorders, it is important to be an advocate for your child whenever you can, such as when working with the health care system and the school system. For example, if your child needs treatment in the emergency room, it is vital to take a copy of your treatment protocol letter with you. Show the letter to the triage nurse and explain what your child needs so that the medical team can understand the next steps and not delay therapy. You can also be an advocate for your child with your health insurer to ensure that medications and other needed treatments are covered (see Working with Insurance Companies). Children diagnosed with fatty acid oxidation disorders may need a medical care plan at school. It is of great value to meet with the school nurse, principal, and your child’s teachers to explain the disorder. It will help them understand what to expect from your child and what accommodations your child may need, such as not being penalized for absences if they are sick.