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Fatty Acid Oxidation Disorders (MCADD, LCHADD, VLCADD)

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Introduction

The Questions and Answers that follow aim to provide an introduction to fatty acid oxidation disorders for parents and other family members. Following those, we offer links to selected resources for more information and support and a list of valuable services.
Note that we use the term doctor to refer to physicians, nurse practitioners, physician assistants, and other licensed clinicians who may care for your child.
More information about many topics relevant to children with fatty acid oxidation disorders and many other chronic conditions and their families can be found in the left menu. Detailed information aimed at primary care doctors can be found in our MCADD, LCHAD/TFP Deficiency, and VLCADD modules. Information can also be found in the Newborn Screening pages MCADD, LCHAD/TFP Deficiency, and VLCADD.

What are fatty acid oxidation disorders (MCADD, LCHADD, VLCADD)?

Fatty acid oxidation disorders are inherited conditions that are quite uncommon. They include MCADD (medium-chain acyl-CoA dehydrogenase deficiency), LCHADD (long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency), and VLCADD (very long-chain acyl-CoA dehydrogenase deficiency). During times of fasting, when the body uses fats as a major source of energy, enzymes break down fatty acids through a process called beta-oxidation. This becomes very important during prolonged fasting and/or periods of increased energy demands (such as fever, stress, or infections). In individuals with these disorders, energy production is impaired, leading to low blood sugar and lethargy (lack of energy), and fatty acids that are not broken down build up in cells. This can cause a number of problems, some of which can be serious or life-threatening. These include metabolic crisis (resulting in low blood sugar, poor organ function and build-up of toxins), cardiac arrhythmia (abnormal heart rhythm), cardiomyopathy (heart muscle disease), muscle pain, and/or myoglobinuria (myoglobin, a protein in heart and skeletal muscles that binds and deliver oxygen, is found in the urine, which can damage the kidney).

How do you get fatty acid oxidation disorders?

Fatty acid oxidation disorders are caused by mutations or changes in a gene, which then cause an enzyme to be defective or not produced. The disorders are a recessive trait, meaning that parents can be carriers without having the disorder themselves. When a child inherits the recessive gene from both parents, the child will have the disorder.

What are the symptoms?

Children with these conditions may have no symptoms when they are healthy and eating well. Symptoms are often brought on by illness and exertion and may become more severe if treatment is not started early, which is more likely if the condition is undiagnosed.
Symptoms differ by type of disorder and by individual, may start anytime between birth and 3 years, and may be mild or severe. Initial symptoms/signs may include:
  • poor feeding
  • vomiting
  • lethargy
  • hypotonia (low muscle tone)
  • hepatomegaly (swelling of the liver)
  • cardiac insufficiency
  • abnormal lab findings: elevated liver and muscle enzymes, increased blood acids, low blood sugar
  • eye problems (may be present in children with LCHADD and VLCADD)
  • rhabdomyolysis (breakdown of muscle tissue that releases a damaging protein into the blood)
Any symptoms need to be monitored by a doctor, and may require treatment in the emergency room. Without effective treatment, complications may include:
  • hepatic (liver) disease
  • cardiomyopathy (heart muscle disease)
  • cardiac conduction defects
  • peripheral neuropathy
  • myopathy
  • seizures
  • brain damage
  • death

How is it diagnosed?

These disorders are usually diagnosed by newborn screening. Analysis of fatty acid beta-oxidation (checking for remnants of the fatty acid breakdown process) in cultured cells, or enzyme activity in cells of the blood, liver, heart, or muscle can be used to confirm the diagnosis. An acylcarnitine profile test may also be used for diagnosis. Additionally, genetic testing may be recommended to identify the type of mutation and help the genetics team create a treatment plan. This testing is usually guided by a metabolic geneticist; the newborn screening program will usually refer parents to such a specialist.

What is the expected outcome?

Children diagnosed with fatty acid oxidation disorders can live fairly normal lives with proper treatment, good nutrition, and management of illnesses. Lifelong management of the disorder is needed. Avoiding episodes of prolonged illness, fasting and dehydration is vital for improving outcomes.
Puberty may be difficult for children with these disorders because the changes in their hormones and bodies require a great deal of energy. Additional support may be needed, along with lifestyle management to ensure they are getting good nutrition.

Will anyone else in the family get a fatty acid oxidation disorder?

All of these disorders are recessive. That means if parents have a child with this condition, both parents are carriers of the abnormal gene and for each subsequent pregnancy there is a
  • 1 in 4 chance of the child having the condition
  • 2 in 4 chance of the child being a carrier
  • 1 in 4 chance of the child not having the gene mutation or the disorder
Unaffected children in the family, as well as extended family members, may choose to be tested 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.

What is the treatment?

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, and dehydration. Intravenous glucose, usually given in an emergency room, is necessary during illness and 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, especially during the first 3-5 years to ensure that children are eating a healthy diet, and to answer questions about nutrition. A heart-healthy diet with complex carbohydrates and proteins is usually recommended, and children should avoid simple carbohydrates unless they are in a crisis.
Some doctors may prescribe medications:
  • Levocarnitine (L-carnitine) can help remove ketones that the body is unable to remove due to an incomplete breakdown of fatty acids.
  • Zofran is an anti-nausea medication that can be used when children are sick and may prevent them from needing treatment in the hospital.

How will my family’s life be changed?

Your family will need to follow strict guidelines on nutrition, illness, and dehydration. Your child may need medications, depending on the enzyme deficiency. 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, such as a glucose IV, to help the medical team understand what needs to be done. 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, the principal, and your child’s teachers to explain the disorder, help them understand what to expect from your child, and talk about any accommodations that may be needed, such as not being penalized for absences if they are sick.

What is beta-oxidation?

Beta-oxidation is a process that breaks down fats:
  • very-long chain fats to long-chain fats, and
  • long-chain fats to medium-chain fats,
eventually resulting in ketone bodies and acetyl-CoA. It involves several enzymes. Mutations in a gene can cause these enzymes to be missing or defective, which causes fatty acid oxidation disorders.

Resources

Information & Support

Where can I go for further information?

For Parents and Patients

Support

Fatty Oxidation Disorders (FOD) Family Support Group
Information for families about fatty acid oxidation disorders, support groups, coping, finances, and links to other sites.

General

An Educator’s Guide to MCADD (PDF Document 2.0 MB)
Contains information to help educators understand MCADD, and can be printed to give to your child’s teacher; Boston Children's Hospital.

VLCADD - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received an initial diagnosis of a newborn disorder; Screening, Technology and Research in Genetics.

Very long-chain acyl-CoA dehydrogenase deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

MCADD - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received an initial diagnosis of this newborn disorder; Screening, Technology and Research in Genetics.

Medium-chain acyl-CoA dehydrogenase deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

MCADD: A Guide for Parents (PacNoRGG) (PDF Document 618 KB)
Eight-page guide that includes an overview, social concerns, sample treatment plan, glossary, regional resources, and references; sponsored by the Pacific Northwest Regional Genetics Group.

LCHAD/TFP Deficiency - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received an initial diagnosis of this newborn disorder; Screening, Technology and Research in Genetics.

Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

Mitochondrial Trifunctional Protein Deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

Services for Patients & Families in Idaho (ID)

For services not listed above, browse our Services categories or search our database.

* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.

Studies

LCHAD/TFP Deficiency in Children (birth-17 years) (ClinicalTrials.gov)
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.

MCADD (clinicaltrials.gov)
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.

Authors & Reviewers

Initial publication: November 2012; last update/revision: July 2020
Current Authors and Reviewers:
Author: Lynne M. Kerr, MD, PhD
Reviewer: Rachel Johnson
Funding: The Medical Home Portal thanks the 2011-2012 URLEND Medical Home Portal trainees group for their contribution to this page.
Authoring history
2016: first version: Natario Couser, MD, MSR; Laurie Smith, MD, Ph.D.R
AAuthor; CAContributing Author; SASenior Author; RReviewer