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Test ID 2OHGP 2-Hydroxyglutaric Aciduria Gene Panel, Varies


Ordering Guidance


The recommended first-tier test for 2-hydroxyglutaric aciduria is urine organic acids; order OAU/Organic Acids Screen, Urine.



Shipping Instructions


Specimen preferred to arrive within 96 hours of collection.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing (Spanish) (T826)

2. Molecular Genetics: Biochemical Disorders Patient Information (T527) in Special Instructions

Useful For

Follow up for abnormal biochemical results suggestive of 2-hydroxyglutaric aciduria

 

Establishing a molecular diagnosis for patients with 2-hydroxyglutaric aciduria

 

Identifying variants within genes known to be associated with 2-hydroxyglutaric aciduria, allowing for predictive testing of at-risk family members

Method Name

Custom Sequence Capture and Targeted Next-Generation Sequencing followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing

Reporting Name

2-OH Glutaric Aciduria Gene Panel

Specimen Type

Varies

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Clinical Information

The 2-hydroxyglutaric aciduria disorders are a group of cerebral organic acidurias that present biochemically with an elevation of 2-hydroxyglutaric acid (2-HG) in the urine. There are two enantiomers or forms of 2-hydroxyglutaric acid, the D-form and the L-form. Depending on the genetic defect, individuals may have an elevation of one or both forms of 2-HG. Routine organic acid analysis (OAU / Organic Acids Screen, Urine), while able to detect 2-HG, is unable to distinguish between the two enantiomers; however, they can be separated with more specialized biochemical testing.

 

L-2-hydroxyglutaric aciduria (L-2-HGA) is caused by defects in L2HGDH and is characterized by progressive cerebellar ataxia and intellectual disability, seizures, and macrocephaly beginning in infancy or early childhood. Symptoms worsen over time leading to severe disability by early adulthood. Magnetic resonance imaging (MRI) findings include subcortical leukoencephalopathy, generalized cerebellar and cerebral atrophy, and atrophy of the corpus callosum.

 

D-2-hydroxylglutaric aciduria (D-2-HGA) is characterized by elevated levels of D-2-hydroxyglutaric acid and typically manifests with developmental delay, seizures, and hypotonia, though can vary widely from asymptomatic to severe. There are 2 types of D-2-HGA depending on the genetic cause. D-2-HGA can either be autosomal recessive, resulting from variants in D2HGDH causing reduced enzymatic activity (Type I) or autosomal dominant gain-of-function variants in IDH2 causing overproduction of D-2-HG (Type II).

 

D,L-2-hydroxylglutaric aciduria is the most severe of the 3 and caused by defects in SLC25A1, which encodes the mitochondrial citrate carrier. It is characterized by neonatal-onset encephalopathy with severe muscular weakness, intractable seizures, respiratory distress, and lack of psychomotor development resulting in early death.

Because of the genetic heterogeneity of the 2-hydroxyglutaric acidurias and the specialized biochemical testing needed to distinguish among the conditions, this genetic panel, which incorporates D2HGDH, L2HGDH, IDH2, and SLC25A1, is an efficient way to diagnose these conditions.

Reference Values

An interpretive report will be provided.

Interpretation

All detected alterations are evaluated according to American College of Medical Genetics and Genomics (ACMG) recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Clinical Reference

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015 May;17(5):405-424

2. Nota B, Struys EA, Pop A, et al: Deficiency in SLC25A1, encoding the mitochondrial citrate carrier, causes combined D-2- and L-2-hydroxyglutaric aciduria. Am J Hum Genet. 2013;92:627-631. doi: 10.1016/j.ajhg.2013.03.009

3. Kranendijk M, Struys EA, van Schaftingen E, et al: IDH2 mutations in patients with D-2-hydroxyglutaric aciduria. Science. 2010 Oct 15;330(6002):336. doi: 10.1126/science.1192632

4. Kranendijk M, Struys EA, Salomons GS, Van der Knaap MS, Jakobs C: Progress in understanding 2-hydroxyglutaric acidurias. J Inherit Metab Dis. 2012;35(4):571-587. doi: 10.1007/s10545-012-9462-5

5. Pop A, Struys EA, Jansen EEW, et al: D-2-hydroxyglutaric aciduria Type I: functional analysis of D2HGDH missense variants. Hum Mutat. 2019; 40(7):975-982. doi: 10.1002/humu.23751

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81479

LOINC Code Information

Test ID Test Order Name Order LOINC Value
2OHGP 2-OH Glutaric Aciduria Gene Panel In Process

 

Result ID Test Result Name Result LOINC Value
608764 Test Description 62364-5
608765 Specimen 31208-2
608766 Source 31208-2
608767 Result Summary 50397-9
608768 Result 82939-0
608769 Interpretation 69047-9
608770 Resources In Process
608771 Additional Information 48767-8
608772 Method 85069-3
608773 Genes Analyzed 48018-6
608774 Disclaimer 62364-5
608775 Released By 18771-6

Day(s) Performed

Varies

Report Available

3 to 4 weeks