Glutaric Acidemia, Type I : GCDH Sequencing

Test Information

GCDH sequencing is a molecular test used to identify variants in the gene associated with Glutaric Acidemia, Type I.

Turnaround Time

2 weeks

CPT Code(s)

81406

Cost

$1,000

Genes

Clinical Information

Glutaric acidemia, type 1 (GA1) is an autosomal recessive inborn error of lysine, hydroxylysine and tryptophan metabolism caused by the deficiency of glutaryl-CoA dehydrogenase (GCDH). Patients are often identified via newborn screening. However, some patients are low excretors and can exhibit normal or mildly elevated biochemical analytes making a definitive diagnosis of GA1 difficult without molecular analysis. GA1 is a neurodegenerative disorder with loss of neurons in the basal ganglia. Clinical features vary, but often include macrocephaly, gait abnormalities, hypotonia, spasms, rigidity and seizures. Retinal or subdural hemorrhages can also occur. Other than possible macrocephaly, patients appear normal at birth. Clinical features are typically preceded by an acute encephalopathic illness with fever before five years of age.

Indications

Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis.

Methodology

Sanger Sequencing

Detection

Sequencing of the gene will detect mutations in 95% of individuals with glutaric acidemia type I.

Associated Tests

Specimen Requirements

5 to 7 ml of peripheral blood collected in an EDTA (lavender top) tube is the preferred specimen type. The minimal blood needed for reliable DNA isolation is 3 ml. Extracted DNA, dried blood spots, and saliva are also accepted for this test.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

Prenatal diagnosis is available if the familial mutations are known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

Molecular Testing, Newborn Screening Follow-Up, Sanger Sequencing
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