SCAD deficiency is inherited in an autosomal recessive pattern. Normally a person has two functioning ACADS genes. In people with SCAD deficiency, both genes have a mutation and there is a deficiency of the critical enzyme activity. Each parent of a newborn with SCAD deficiency typically has one functional and one mutated gene and is considered a carrier. When both parents are carriers, the chance of a newborn inheriting two mutated genes is 25%.
Carriers of SCAD deficiency do not typically have symptoms.
Neonates with SCAD deficiency are usually asymptomatic and there is a range of symptoms in older individuals. Many people with SCAD deficiency never develop symptoms. Possible symptoms include hypoglycemia, failure to thrive, microcephaly (small head size), hypotonia (low muscle tone), developmental delay, feeding difficulties and seizures. The symptoms are extremely variable, even within the same family.
- Incidence: The overall incidence is approximately 1 in 40,000 to 1 in 100,000.
- New York State Method of Screening (First Tier): Screening for SCAD deficiency is accomplished by measuring an acylcarnitine (C4) by tandem mass spectrometry (MS/MS).
- Second Tier Screening: None
- Testing can be affected by: None known.
- Interpretation/reporting of data: Results are reported as within acceptable limits, borderline or as a referral. A repeat specimen should be collected for a borderline result. Prompt consultation with a specialist is required for a referral.
- Referral to Specialty Care Center: Patients with an abnormal newborn screen for SCAD deficiency are referred to an Inherited Metabolic Disorder Specialty Care Center for evaluation by a biochemical geneticist trained in the diagnosis and treatment of SCAD deficiency.
Diagnostic testing includes quantification of plasma acylcarnitines, urine organic acids, and urine acylglycines. Molecular genetic testing of the ACADS gene may be used for confirmation of the diagnosis.
There is no cure for this disorder. The need for treatment is unclear, but may include avoidance of fasting. During times of illness, care givers and health care providers should be aware of an increased risk for hypoglycemia, metabolic acidosis and dehydration.
Prognosis is variable and dependent on multiple factors including the severity of disease.
Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a fatty acid oxidation disorder (inherited metabolic disorder).
SCAD deficiency is caused by mutations in the ACADS gene. Individuals with this disorder are unable to convert certain fats to energy and may have symptoms during times of high energy need such as when fasting or ill.