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Test ID: SCADK    
Short-Chain Acyl-CoA Dehydrogenase (SCAD) Deficiency, Known Mutation

Useful For Suggests clinical disorders or settings where the test may be helpful

Confirmation of diagnosis of short-chain acyl-CoA dehydrogenase (SCAD) deficiency (as a follow-up to the biochemical analyses) for individuals from families in which known familial mutations has been previously identified

 

Carrier screening for individuals at risk for a known familial SCAD gene mutation

Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request

Documentation of the specific familial mutation must be provided with the specimen in order to perform this test.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Short-chain acyl-CoA dehydrogenase (SCAD) catalyzes the first step in the mitochondrial beta-oxidation of fatty acids with a chain length of 6 to 4 carbons. SCAD deficiency is a rare autosomal recessive condition. The clinical phenotype of SCAD shows considerable variability and is incompletely defined. Of those reported cases, hypoglycemia, developmental delay, and muscle hypotonia are the most common indicated features. The diagnosis of SCAD deficiency is challenging and should be based on the clinical presentation, 2 or more findings of ethylmalonic aciduria, and determination of fatty acid flux in fibroblasts indicating deficient SCAD activity. Molecular genetic analysis of the gene associated with SCAD (ACADS) may confirm the biochemical phenotype of SCAD deficiency.

 

The first step in evaluation for SCAD deficiency is identification of 2 or more findings of ethylmalonic aciduria, as determined by either OAU / Organic Acids Screen, Urine or ACYLG / Acylglycines, Quantitative, Urine. Ethylmalonic aciduria is a common, although not specific, laboratory finding in patients with SCAD deficiency. Determination of fatty acid flux in fibroblasts (FAO / Fatty Acid Oxidation Probe Assay, Fibroblast Culture) is warranted for an individual with 2 or more findings of ethylmalonic aciduria.

 

DNA sequencing of the ACADS gene is typically utilized only when SCAD deficiency is identified through biochemical analysis. The ACADS gene is located on chromosome 12q22 and consists of 10 exons. Molecular genetic studies revealed that some patients carry ACADS gene mutations that cause complete absence of SCAD activity, while others carry ACADS gene variants (511C->T;625G->A) that may confer disease susceptibility only in association with other factors. The allele frequencies in the general population of the 511C->T and 625G->A gene variants are 3% and 22%, respectively. The presence of 2 of these gene variants are not considered an independent diagnostic marker for SCAD deficiency. Although further investigation is needed, it is most likely that these variants are not clinically significant.

 

Identification of 2 ACADS gene mutations that cause complete absence of SCAD activity alone is not sufficient to explain or determine possible clinical phenotype or prognosis. The clinical significance of carrying 2 mutations is often uncertain. Therefore, the results of ACADS gene sequencing for SCAD deficiency should be interpreted in light of the clinical presentation and biochemical findings in each case.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The identification of a disease-causing mutation in an affected family member is necessary before predictive testing for other family members can be offered. If a familial mutation has not been previously identified, order SCADM / Short-Chain Acyl-CoA Dehydrogenase (SCAD) Deficiency, Mutation Screen.

 

Analysis is performed for the familial mutations provided only. This assay does not rule out the presence of other mutations within this gene or within other genes that may be associated with metabolic disease.

 

We strongly recommend that patients undergoing predictive testing receive genetic counseling both prior to testing and after results are available.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Any error in the diagnosis or in the pedigree provided to us, including false paternity, could lead to an erroneous interpretation of results.

 

A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Nagan N, Kruckeberg KE, Tauscher AL, et al: The frequency of short-chain acyl-CoA dehydrogenase gene variants in the US population and correlation with the C4-acylcarnitine concentration in newborn blood spots. Mol Genet Metab 2003 April;78:239-246

2. Corydon MJ, Vockley J, Rinaldo P, et al: Role of common gene variations in the molecular pathogenesis of short-chain acyl-CoA dehydrogenase deficiency. Pediatr Res 2001 January;49(1):18-23

3. van Maldegem BT, Duran M, Wanders RJ, et al: Clinical, biochemical, and genetic heterogeneity in short-chain acyl-coenzyme A dehydrogenase deficiency. JAMA 2006 August;296(8):943-952

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test