Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is a condition that prevents the body from converting certain fats into energy, particularly during periods without food (fasting).

There are three forms of VLCAD deficiency, and they are defined by when the signs and symptoms of the condition begin. The early-onset form is the most severe and begins in infancy. Signs and symptoms can include lack of energy (lethargy) and muscle weakness. People with VCLAD deficiency can have low blood sugar (glucose), known as hypoglycemia. Affected individuals are also at risk for serious complications such, as liver abnormalities and life-threatening heart problems. 

Individuals with childhood-onset VLCAD deficiency typically experience an enlarged liver (hepatomegaly) and low blood glucose. This form is sometimes referred to as the hepatic or hypoketotic hypoglycemic form because of these signs. Additional signs and symptoms include other liver problems or muscle weakness.

The adult-onset form, which begins in adolescence or adulthood, usually involves muscle pain and the breakdown of muscle tissue (rhabdomyolysis). The destruction of muscle tissue releases a large amount of a protein called myoglobin, which is processed by the kidneys and released in the urine (myoglobinuria). Myoglobinuria causes the urine to be red or brown.

In both children and adults, problems related to VLCAD deficiency can be triggered by periods of fasting, illness, exercise, and exposure to hot or cold temperatures. In children, this disorder is sometimes mistaken for Reye syndrome, a severe disorder that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome occur in children who take aspirin during these viral infections.

VLCAD deficiency is estimated to affect 1 in 40,000 to 120,000 people.

Variants (also called mutations) in the ACADVL gene cause VLCAD deficiency. This gene provides instructions for making an enzyme called very long-chain acyl-CoA dehydrogenase, which is required to break down (metabolize) a group of fats called very long-chain fatty acids. These fatty acids are found in foods and the body's fat tissues. Fatty acids are a major source of energy for the heart and muscles. During periods of fasting, fatty acids are also an important energy source for the liver and other tissues.

Variants in the ACADVL gene lead to a shortage (deficiency) of the VLCAD enzyme within cells. When cells do not have enough of this enzyme, very long-chain fatty acids are not broken down properly. As a result, these fats are not converted to energy, which can lead to signs and symptoms of the disorder such as lethargy and hypoglycemia. Very long-chain fatty acids or partially metabolized fatty acids may also build up in tissues and damage the heart, liver, and muscles. This abnormal buildup causes the other signs and symptoms of VLCAD deficiency.

Genetic Testing Information

• Genetic Testing Registry: Very long chain acyl-CoA dehydrogenase deficiency

Genetic and Rare Diseases Information Center

• Very long chain acyl-CoA dehydrogenase deficiency

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Clinical Trials

• ClinicalTrials.gov

Catalog of Genes and Diseases from OMIM

• ACYL-CoA DEHYDROGENASE, VERY LONG-CHAIN, DEFICIENCY OF; ACADVLD

Scientific Articles on PubMed

• PubMed

• Diekman EF, Ferdinandusse S, van der Pol L, Waterham HR, Ruiter JP, Ijlst L, Wanders RJ, Houten SM, Wijburg FA, Blank AC, Asselbergs FW, Houtkooper RH, Visser G. Fatty acid oxidation flux predicts the clinical severity of VLCAD deficiency. Genet Med. 2015 Dec;17(12):989-94. doi: 10.1038/gim.2015.22. Epub 2015 Apr 2. Citation on PubMed
• Evans M, Andresen BS, Nation J, Boneh A. VLCAD deficiency: Follow-up and outcome of patients diagnosed through newborn screening in Victoria. Mol Genet Metab. 2016 Aug;118(4):282-7. doi: 10.1016/j.ymgme.2016.05.012. Epub 2016 May 16. Citation on PubMed
• Laforet P, Acquaviva-Bourdain C, Rigal O, Brivet M, Penisson-Besnier I, Chabrol B, Chaigne D, Boespflug-Tanguy O, Laroche C, Bedat-Millet AL, Behin A, Delevaux I, Lombes A, Andresen BS, Eymard B, Vianey-Saban C. Diagnostic assessment and long-term follow-up of 13 patients with Very Long-Chain Acyl-Coenzyme A dehydrogenase (VLCAD) deficiency. Neuromuscul Disord. 2009 May;19(5):324-9. doi: 10.1016/j.nmd.2009.02.007. Epub 2009 Mar 26. Citation on PubMed
• Miller MJ, Burrage LC, Gibson JB, Strenk ME, Lose EJ, Bick DP, Elsea SH, Sutton VR, Sun Q, Graham BH, Craigen WJ, Zhang VW, Wong LJ. Recurrent ACADVL molecular findings in individuals with a positive newborn screen for very long chain acyl-coA dehydrogenase (VLCAD) deficiency in the United States. Mol Genet Metab. 2015 Nov;116(3):139-45. doi: 10.1016/j.ymgme.2015.08.011. Epub 2015 Sep 2. Citation on PubMed or Free article on PubMed Central
• Pena LD, van Calcar SC, Hansen J, Edick MJ, Walsh Vockley C, Leslie N, Cameron C, Mohsen AW, Berry SA, Arnold GL, Vockley J; IBEMC. Outcomes and genotype-phenotype correlations in 52 individuals with VLCAD deficiency diagnosed by NBS and enrolled in the IBEM-IS database. Mol Genet Metab. 2016 Aug;118(4):272-81. doi: 10.1016/j.ymgme.2016.05.007. Epub 2016 May 13. Citation on PubMed or Free article on PubMed Central
• Spiekerkoetter U, Sun B, Zytkovicz T, Wanders R, Strauss AW, Wendel U. MS/MS-based newborn and family screening detects asymptomatic patients with very-long-chain acyl-CoA dehydrogenase deficiency. J Pediatr. 2003 Sep;143(3):335-42. doi: 10.1067/S0022-3476(03)00292-0. Citation on PubMed