Short-chain acyl-CoA dehydrogenase deficiency
Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an inherited metabolic disorder that prevents the body from converting certain fats into energy. Symptoms can range from mild to severe and are often triggered by fasting or illness.
Overview
Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a condition that prevents the body from converting specific fats into energy, particularly during periods without food (fasting). The severity of this condition varies widely, even among members of the same family. While some individuals experience symptoms in infancy or adulthood, others are diagnosed through laboratory testing but never develop any symptoms of the condition.
Symptoms
The signs and symptoms of SCAD deficiency can present at different stages of life and are often triggered by fasting or viral infections.
Infancy and Early Childhood
- Vomiting
- Low blood glucose (hypoglycemia)
- A lack of energy (lethargy)
- Poor feeding and failure to gain weight and grow at the expected rate (failure to thrive)
- Poor muscle tone (hypotonia)
- Seizures
- Developmental delay
- A small head size
In children, this disorder is sometimes mistaken for Reye syndrome, a severe condition that can develop while recovering from viral infections like chickenpox or flu, often associated with aspirin use.
Adulthood
- Muscle weakness
- Muscle wasting
Frequency
This disorder is estimated to affect approximately 1 in 35,000 to 50,000 newborns.
Causes
SCAD deficiency is caused by mutations in the ACADS gene. This gene provides instructions for making an enzyme called short-chain acyl-CoA dehydrogenase, which is required to metabolize a group of fats known as short-chain fatty acids.
Fatty acids serve as a major source of energy for the heart and muscles, and they are crucial for the liver and other tissues during periods of fasting. Mutations in the ACADS gene lead to a shortage of the SCAD enzyme within cells. Without enough of this enzyme, short-chain fatty acids are not properly converted into energy, leading to symptoms such as lethargy, hypoglycemia, and muscle weakness. It is not yet fully understood why some individuals with the deficiency remain completely asymptomatic.
Associated Genes
- ACADS
Inheritance
This condition is inherited in an autosomal recessive pattern, meaning both copies of the gene in each cell must have mutations to cause the disorder. The parents of an affected individual typically carry one copy of the mutated gene but do not show signs or symptoms of the condition.
Other Names for This Condition
- ACADS deficiency
- Deficiency of butyryl-CoA dehydrogenase
- Lipid-storage myopathy secondary to short-chain acyl-coa dehydrogenase deficiency
- SCAD deficiency
- SCADH deficiency
- Short-chain acyl-coenzyme A dehydrogenase deficiency
Additional Resources
- Genetic Testing Registry: Deficiency of butyryl-CoA dehydrogenase
- Genetic and Rare Diseases Information Center: Short chain acyl-CoA dehydrogenase deficiency
- National Organization for Rare Disorders (NORD)
- OMIM: ACYL-CoA DEHYDROGENASE, SHORT-CHAIN, DEFICIENCY OF; ACADSD
- PubMed