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PubMed This is a summary of 67 peer-reviewed journal articles Updated
Medical Genetics · Very Long-Chain Acyl-CoA Dehydrogenase Deficiency

Very long chain acyl-CoA dehydrogenase deficiency (VLCADD): A Patient Guide

At a Glance

VLCADD makes it hard for the body to use long-chain fats for energy, so avoiding fasting is central to care. Individualized feeding schedules, specialized formulas or medium-chain fats, emergency illness plans, and metabolic-team monitoring help reduce risk and support active lives.

Very Long-Chain Acyl-CoA Dehydrogenase Deficiency (VLCADD) is a rare genetic condition that changes how the body creates energy from the food we eat. Specifically, the body lacks enough of a specialized protein, or enzyme, needed to break down a certain type of fat known as long-chain fatty acids [1]. Under normal circumstances, the body burns sugar (glucose) for fuel, but when that sugar runs out—such as during sleep, periods of illness, or intense exercise—the body naturally switches to burning its fat stores. For a person with VLCADD, this switch reveals an impaired pathway; the body cannot access the energy it needs, and catabolism (fat breakdown) can cause harmful metabolites to accumulate in the heart, liver, and muscles [2][3].

The way VLCADD behaves can look very different from one person to the next. Some individuals have a severe form that appears shortly after birth and may affect the heart, while others have a milder form that may not cause noticeable symptoms until later in childhood or even adulthood, primarily affecting muscle strength and endurance [4][5]. Because the genetic results alone do not always predict how a person will feel, doctors sometimes use specialized functional tests to measure the remaining fat-burning capacity in the cells. While these results cannot perfectly predict the future, they can support diagnosis and risk assessment, helping the medical team determine how intensive the daily management needs to be [6][7].

The cornerstone of living with VLCADD is a proactive approach to energy management. The most important goal is to prevent the body from entering a fasting state where it is forced to rely on fat for fuel. This is achieved primarily through the strict avoidance of fasting (going too long without food) and by providing alternative fuel sources, such as specialized formulas or medium-chain fats that the body can process more easily [8][9]. By maintaining a consistent intake of energy-rich foods and following an individualized feeding schedule, families can help ensure that the body always has the fuel it needs to function safely [3].

Navigating a VLCADD diagnosis is a collaborative journey that involves a specialized metabolic care team, including geneticists and dietitians. This team works closely with parents to create a tailored daily diet and a clear emergency protocol to follow during times of illness or physical stress [10]. While the diagnosis brings new responsibilities and a need for lifelong monitoring, early detection through newborn screening has fundamentally changed the outlook for these individuals. With the right support and preventive care, many children with VLCADD can lead active, full lives, supported by a care plan that is built specifically for their unique needs [6][11].

In this guide

6 chapters

01

Starting Your Journey: Understanding the Initial Screen

Learn what a positive VLCADD newborn screen means, which follow-up tests to expect, and why prompt feeding guidance matters while your baby is evaluated.

02

The Science of VLCADD: From Genes to Diagnosis

Learn how VLCADD affects fat breakdown and how C14:1 screening, ACADVL gene testing, and functional assays help confirm a diagnosis and guide care for babies.

03

Understanding the Different Forms of VLCADD

Learn how VLCADD forms differ by age, symptoms, heart, liver, and muscle effects, newborn screening, and LC-FAO flux testing used to guide care decisions.

04

Daily Care: Fueling the Body and Preventing Crisis

Learn daily VLCADD care for your child, including safe fasting limits, MCT oil and meal planning, exercise precautions, and crisis prevention during illness.

05

Emergency Preparedness: Recognizing and Treating a Crisis

Learn to prevent and respond to very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) crises, including sick-day rules, red flags, ER care, IV glucose.

06

Staying Ahead: Long-Term Monitoring and Wellness

Learn how long-term VLCADD monitoring protects your child’s heart, muscles, growth, nutrition, and wellbeing, including ECGs, labs, and care transition.

Common questions in this guide

What is VLCADD, and why does it affect energy?
VLCADD is a rare inherited condition in which the body does not have enough of an enzyme to break down long-chain fats for energy. When the body's usual sugar fuel runs low during fasting, illness, or intense exercise, it may not switch safely to fat for fuel.
Why must people with VLCADD avoid fasting?
Going too long without food forces the body to use stored fat, which it cannot process normally in VLCADD. This can leave the body short of energy and allow harmful substances to build up, especially during illness or physical stress.
How is VLCADD confirmed after a newborn screening result?
Confirmation may combine genetic results with specialized functional tests that measure how well cells can use fat for energy. Newborn screening helps identify the condition early, and the metabolic team uses the results with the person's symptoms and history to plan care and assess risk.
Does VLCADD look the same in everyone?
No. A severe form can appear soon after birth and affect the heart, while a milder form may first become noticeable in later childhood or adulthood through reduced muscle strength or exercise endurance. Genetic results alone may not predict how VLCADD will affect a person.
What does daily care for VLCADD involve?
Daily care focuses on preventing fasting through a consistent, individualized feeding schedule. Some people also need specialized formulas or medium-chain fats, with guidance from a metabolic care team that may include a geneticist and dietitian.
What should we do if someone with VLCADD becomes ill or cannot keep food down?
Follow the emergency protocol created by the metabolic care team and contact the team promptly for instructions. Illness and physical stress can increase the risk of energy problems, so the plan may specify alternative fuel and when urgent medical care is needed.
Can people with VLCADD live active lives?
With early detection, preventive care, and an individualized plan, many children with VLCADD can lead active, full lives. Ongoing monitoring and following the feeding and illness plan are important because the condition requires lifelong management.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on our initial results, where does my child currently fall on the spectrum of VLCADD severity?
  2. 2.What is the single most important 'rule' we must follow regarding feeding and fasting right now?
  3. 3.How will our metabolic care team help us translate these medical concepts into a safe daily routine at home?
  4. 4.What are the next steps in our diagnostic journey to move from a 'suspected' case to a confirmed care plan?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (11)
  1. 1

    Very-Long-Chain Acyl-CoA Dehydrogenase Deficiency: Family Impact and Perspectives.

    Crawford S, Sablon E, Ali N, et al.

    International journal of neonatal screening 2023; (9(4)) doi:10.3390/ijns9040053.

    PMID: 37873844
  2. 2

    Recent Advances in the Pathophysiology of Fatty Acid Oxidation Defects: Secondary Alterations of Bioenergetics and Mitochondrial Calcium Homeostasis Caused by the Accumulating Fatty Acids.

    Amaral AU, Wajner M

    Frontiers in genetics 2020; (11()):598976 doi:10.3389/fgene.2020.598976.

    PMID: 33329744
  3. 3

    Fasting induces prominent proteomic changes in liver in very long chain Acyl-CoA dehydrogenase deficient mice.

    Wang W, Palmfeldt J, Mohsen AW, et al.

    Biochemistry and biophysics reports 2016; (8()):333-339 doi:10.1016/j.bbrep.2016.08.014.

    PMID: 28955973
  4. 4

    Fatty acid oxidation flux predicts the clinical severity of VLCAD deficiency.

    Diekman EF, Ferdinandusse S, van der Pol L, et al.

    Genetics in medicine : official journal of the American College of Medical Genetics 2015; (17(12)):989-94 doi:10.1038/gim.2015.22.

    PMID: 25834949
  5. 5

    Impact of newborn screening for very-long-chain acyl-CoA dehydrogenase deficiency on genetic, enzymatic, and clinical outcomes.

    Bleeker JC, Kok IL, Ferdinandusse S, et al.

    Journal of inherited metabolic disease 2019; (42(3)):414-423 doi:10.1002/jimd.12075.

    PMID: 30761551
  6. 6

    Management and diagnosis of mitochondrial fatty acid oxidation disorders: focus on very-long-chain acyl-CoA dehydrogenase deficiency.

    Yamada K, Taketani T

    Journal of human genetics 2019; (64(2)):73-85 doi:10.1038/s10038-018-0527-7.

    PMID: 30401918
  7. 7

    Direct Prediction of VLCADD Severity Using Newborn Screening Analyte Data.

    Schwantje M, Maase RE, Dekkers E, et al.

    Journal of inherited metabolic disease 2026; (49(2)):e70143 doi:10.1002/jimd.70143.

    PMID: 41702539
  8. 8

    Very long-chain acyl-CoA dehydrogenase (VLCAD-) deficiency-studies on treatment effects and long-term outcomes in mouse models.

    Tucci S

    Journal of inherited metabolic disease 2017; (40(3)):317-323 doi:10.1007/s10545-017-0016-8.

    PMID: 28247148
  9. 9

    Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach.

    Van Calcar SC, Sowa M, Rohr F, et al.

    Molecular genetics and metabolism 2020; (131(1-2)):23-37 doi:10.1016/j.ymgme.2020.10.001.

    PMID: 33093005
  10. 10

    Expert consensus on diagnosis and treatment of very long-chain acyl-CoA dehydrogenase deficiency.

    Division of Biochemistry and Metabolism, Medical Genetics Branch, Chinese Medical Association , Division of Genetics and Metabolism, Child Diseases and Health Care Branch, Chinese Association for Maternal and Child Health

    Zhejiang da xue xue bao. Yi xue ban = Journal of Zhejiang University. Medical sciences 2022; (51(1)):122-128 doi:10.3724/zdxbyxb-2022-0107.

    PMID: 36161784
  11. 11

    Screening for Life: Perspectives From Adult Metabolic Specialists on Newborn Screening for Inherited Metabolic Diseases.

    Langeveld M, Sirrs S, Schoenmakers DH, et al.

    Journal of inherited metabolic disease 2025; (48(4)):e70057 doi:10.1002/jimd.70057.

    PMID: 40610367

This VLCADD page is for informational purposes only and does not constitute medical advice. Your metabolic care team should provide the individualized feeding schedule and emergency instructions for your child or your own care.

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