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Fatty Acid Oxidation Disorders (MCADD, LCHADD, VLCADD)

Introduction

Here you’ll find answers to some of the questions that parents often have about this condition. Additional resources are listed at the bottom of the page. Diagnosis and management information can be found in the MCADD, LCHADD/TFP Deficiency,and VLCADD modules, which are written for primary care clinicians but also may be of help to parents and family members. Information can also be found in the Newborn Screening pages MCADD, LCHADD/TFP Deficiency, and VLCADD.

What are fatty acid oxidation disorders (MCADD, LCHADD, VLCADD) and what causes them?

MCADD (medium-chain acyl-CoA dehydrogenase deficiency), LCHADD (long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency), and VLCADD (very long-chain acyl-CoA dehydrogenase deficiency) are disorders of fatty acid oxidation. During times of fasting, the body uses fats as a major source of energy, breaking them down through a process called beta-oxidation. This process involves several enzymes that break down very-long chain fats to long-chain fats and long-chain fats to medium-chain fats, eventually resulting in ketone bodies and acetyl-CoA. Enzymes called dehydrogenases are needed to break down and use fats with large numbers of carbons. Fatty acids are generally used during prolonged fasting and/or periods of increased energy demands (e.g., fever, stress, infections). In these conditions, energy production is impaired, leading to hypoglycemia (low blood sugar) and lethargy (lack of energy), and fatty acids that are not broken down accumulate in cells, causing metabolic crisis, cardiac arrhythmia (abnormal heart rhythm), cardiomyopathy, muscle pain, and/or myoglobinuria (myoglobin, a protein in heart and skeletal muscles that binds and deliver oxygen, present in the urine).

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

Symptoms vary, and may begin 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 (abnormal enlargement of the liver)
  • cardiac insufficiency
  • lab findings: elevated liver function tests, elevated CK, metabolic acidosis, lactic acidosis, hypoglycemia
Without effective treatment, subsequent complications may include:
  • hepatic disease
  • cardiomyopathy
  • 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 in cultured fibroblasts or enzyme activity in leukocytes, fibroblasts, liver, heart, or skeletal muscle can be used to confirm the diagnosis if it remains in question.

What is the prognosis?

Good, if episodes of prolonged illness, fasting and dehydration can be avoided.

What is the risk for other family members or future babies?

All of these disorders are autosomal recessive. That means if parents have a child with this condition, there is a 1 in 4 chance of having another child with this condition with each subsequent pregnancy.

What treatments/therapies/medications are recommended or available?

After diagnosis, the main goal of treatment is to avoid progression of the disease and acute decompensations brought about by illness, fasting and dehydration. IV glucose is necessary during illness and dehydration. The metabolic geneticist, your child's primary medical home, and your family should have a written plan in place for acute illnesses.

How will my child and our family be impacted?

Your family will need to follow strict guidelines with regard to illness and dehydration, and may need medications, depending on the enzyme deficiency. Support groups may be helpful.

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

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.

VLCADD (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; sponsored by the U.S. 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.

MCADD (Genetics Home Reference)
Excellent, detailed review of MCADD for patients and families; sponsored by the U.S. 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.

LCHADD/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.

LCHADD (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; sponsored by the U.S. National Library of Medicine.

Trifunctional Protein Deficiency (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; sponsored by the U.S. National Library of Medicine.

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Authors

Author: Lynne M Kerr, MD, PhD - 11/2012
Reviewing Authors: Natario Couser, MD, MS - 5/2016
Laurie Smith, MD, PhD - 5/2016
Compiled and edited by: URLEND Trainees, 2011-2012 - 11/2012
Content Last Updated: 5/2016

Funding/Support

The Medical Home Portal thanks the 2011-2012 URLEND Medical Home Portal trainees group for their contribution to this page.