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Short-chain acyl-CoA dehydrogenase deficiency
(often shortened to SCAD deficiency)
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Reviewed May 2015
What is SCAD deficiency?
Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a condition that prevents the body from converting certain fats into energy, especially during periods without food (fasting).
Signs and symptoms of SCAD deficiency may appear during infancy or early childhood and can include vomiting, low blood sugar (hypoglycemia), a lack of energy (lethargy), poor feeding, and failure to gain weight and grow at the expected rate (failure to thrive). Other features of this disorder may include poor muscle tone (hypotonia), seizures, developmental delay, and a small head size (microcephaly).
The symptoms of SCAD deficiency may be triggered by fasting or illnesses such as viral infections. This disorder is sometimes mistaken for Reye syndrome, a severe condition 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 are associated with the use of aspirin during these viral infections.
In some people with SCAD deficiency, signs and symptoms do not appear until adulthood. These individuals are more likely to have problems related to muscle weakness and wasting.
The severity of this condition varies widely, even among members of the same family. Some individuals are diagnosed with SCAD deficiency based on laboratory testing but never develop any symptoms of the condition.
How common is SCAD deficiency?
This disorder is thought to affect approximately 1 in 35,000 to 50,000 newborns.
What genes are related to SCAD deficiency?
Mutations in the ACADS gene cause SCAD deficiency. This gene provides instructions for making an enzyme called short-chain acyl-CoA dehydrogenase, which is required to break down (metabolize) a group of fats called short-chain fatty acids. 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.
Mutations in the ACADS gene lead to a shortage (deficiency) of the SCAD enzyme within cells. Without sufficient amounts of this enzyme, short-chain fatty acids are not metabolized properly. As a result, these fats are not converted into energy, which can lead to the signs and symptoms of this disorder, such as lethargy, hypoglycemia, and muscle weakness. It remains unclear why some people with SCAD deficiency never develop any symptoms.
Read more about the ACADS gene.
How do people inherit SCAD deficiency?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of SCAD deficiency?
These resources address the diagnosis or management of SCAD deficiency and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about SCAD deficiency?
You may find the following resources about SCAD deficiency helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for SCAD deficiency?
What if I still have specific questions about SCAD deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding SCAD deficiency?
acids ; aciduria ; autosomal ; autosomal recessive ; carnitine ; cell ; CoA ; coenzyme A ; deficiency ; dehydrogenase ; developmental delay ; enzyme ; failure to thrive ; fasting ; fatty acids ; gene ; hypoglycemia ; hypotonia ; inherited ; lethargy ; lipid ; microcephaly ; muscle tone ; newborn screening ; recessive ; screening ; syndrome ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (10 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.