ARX-Related Disorders (ARX Known Mutation)
- Synonyms: X-linked lissencephaly with abnormal genitalia (XLAG), West syndrome, ISSX1, EIEE1, Partington Syndrome, X-linked Mental Retardation, X-linked Infantile Spasms
- LIS Mnemonic: MBARXKNWN
Collect
Collect whole blood in a purple top (EDTA) tube.
Volume Required
3 ml
Minimum Required
3 ml
Transport
Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.
Stability
Whole blood can be refrigerated until shipment.
Unacceptable conditions
Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.
Specimen Handling
Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.
Days Performed
Mon - Fri 9:00am to 4:00pm
Reported
2-3 weeks
CPT
81403
Disease Information
Clinical Features:
Mutations in the ARX gene lead to different nonsyndromic as well as syndromic forms of mental retardation: Partington syndrome (PRTS), X-linked infantile spasms syndrome (ISSX), X-linked lissencephaly with abnormal genitalia (XLAG), X-linked myoclonic epilepsy with spasticity and intellectual disability (XMESID), and non syndromic X-linked mental retardation (MRX). More recently, ARX mutations have been identified in several women with isolated agenesis of the corpus callosum (Proud syndrome) and in men with hydranencephaly.
Molecular Genetics:
ARX is located on Xp22 and contains 5 coding exons. ARX belongs to the Aristaless-related Paired-class homeodomain protein family and acts as a transcription factor involved in the organization of primary axes in a developing embryo. Mutations identified in ARX have included polyalanine repeat tract expansions, missense mutations, nonsense mutations, premature termination mutations, frameshift mutations, splice site mutations, duplications/insertions, and large deletions.
Test Methods:
Sequence analysis of the mutation previously identified in a family member will be performed.
Detection Rate:
The analytical sensitivity of this assay is ~99%.
Related Tests:
Prenatal testing is available to adult females who are confirmed carriers of mutations. Please contact the laboratory director to discuss appropriate testing prior to collecting a prenatal specimen.
Results:
Test results with interpretation will be mailed and/or faxed to the referring physician or laboratory following completion of the test. Additional reports will be provided as requested.
Utility:
The clinical utility of such testing is to support a clinical diagnosis of the disease, facilitate genetic counseling, assess the risk to other first degree relatives and to facilitate testing of at - risk family members.
Remarks
Whole blood in EDTA purple top tubes is the preferred sample. High molecular weight genomic DNA, cheek epithelial cells, or other samples containing DNA may be acceptable. Contact the laboratory for specific instructions regarding such samples before sending the sample.
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