Glutaric Acidemia Type I: GCDH Sequencing

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

• Glutaric Acidemia type 1 (GA1)

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.

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.

Sanger Sequencing

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

The preferred sample type is 3-5 ml of peripheral blood collected in an EDTA (purple top) tube. Extracted DNA, dried blood spots, and saliva are also accepted for this test. Saliva samples must be submitted in an approved saliva kit. Contact the lab to receive a saliva kit or to have one sent to your patient.

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 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.