Deafness, Autosomal Recessive 24 (DFNB24) via the RDX Gene
Summary and Pricing 
Test Method
Exome Sequencing with CNV Detection
| Test Code | Test Copy Genes | Test CPT Code | Gene CPT Codes Copy CPT Code | Base Price | |
|---|---|---|---|---|---|
| 8169 | RDX | 81479 | 81479,81479 | $990 | Order Options and Pricing |
Pricing Comments
Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.
An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.
Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).
Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).
The Sanger Sequencing method for this test is NY State approved.
For Sanger Sequencing click here.Turnaround Time
3 weeks on average for standard orders or 2 weeks on average for STAT orders.
Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.
Targeted Testing
For ordering sequencing of targeted known variants, go to our Targeted Variants page.
Clinical Features and Genetics
Clinical Features
Autosomal recessive deafness 24 (DFNB24) is a nonsyndromic form of hereditary sensorineural hearing loss that is caused by a decay in the cytoskeletal protein known as radixin (Khan et al. 2007; Shearer et al. 2009; Miyagawa et al. 2013). This protein is present in the hair bundles of the inner ear hair cells and may play a role in linking the cytoskeletal protein actin to the plasma membrane (Pataky et al. 2004). DFNB24 is characterized by the progressive degeneration of cochlear stereocilia, which results in a dysfunctional transmission of sound vibrations across the auditory canal, specifically the organ of Corti and the vestibular system (Kitajiri et al. 2004). This form of hearing loss is generally prelingual and often results in severe-to-profound hearing loss. Because radixin is also a dominant protein in the liver, individuals with DFNB4 may also show signs of mild liver injury such as hyperbilirubinemia.
Genetics
Autosomal recessive DFNB24 is caused by mutations in the radixin (RDX) gene, which has been localized on chromosomal region 11q22.3 and consists of 14 exons (Wilgenbus et al. 1993). The sequence of the protein product radixin is highly similar to that of ezrin and moesin, which are paralogous proteins that constitute the ezrin, radixin, and moesin (ERM) family that functions as a cross-linker between integral membrane proteins and cytoskeletal actin filaments. The radixin protein is 583 amino acids in length and has a molecular weight of 68 kDa. About 5 causative variants have been reported to date in the RDX gene, which include missense variants, splicing variants, and small insertions (Khan et al. 2007; Shearer et al. 2009; Miyagawa et al. 2013).
Reports describe causative RDX variants in large, consanguineous Pakistani and Iranian families with autosomal recessive nonsyndromic hearing loss (ARNSHL), with affected family members observed at the fourth to seventh generations (Khan et al. 2007; Shearer et al. 2009; Lee et al. 2011).
Clinical Sensitivity - Sequencing with CNV PGxome
In an extensive molecular epidemiology study that involved screening of 112 hearing loss candidate genes in 216 randomly selected Japanese deafness patients, a pathogenic variant in the RDX gene was identified in one early-onset hearing loss patient (Miyagawa et al. 2013).
Testing Strategy
This test provides full coverage of all coding exons of the RDX gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).
Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).
Indications for Test
The ideal RDX test candidates are individuals who present with prelingual, bilateral, severe-to-profound hearing loss, and hyperbilirubinemia. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in RDX.
The ideal RDX test candidates are individuals who present with prelingual, bilateral, severe-to-profound hearing loss, and hyperbilirubinemia. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in RDX.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| RDX | 179410 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Deafness, Autosomal Recessive 24 | AR | 611022 |
Citations
- Khan SY, Ahmed ZM, Shabbir MI, Kitajiri S, Kalsoom S, Tasneem S, Shayiq S, Ramesh A, Srisailpathy S, Khan SN, Smith RJH, Riazuddin S, Friedman TB, Riazuddin S. 2007. Mutations of the RDX gene cause nonsyndromic hearing loss at the DFNB24 locus. Human Mutation 28: 417-423. PubMed ID: 17226784
- Kitajiri S, Fukumoto K, Hata M, Sasaki H, Katsuno T, Nakagawa T, Ito J, Tsukita S, Tsukita S. 2004. Radixin deficiency causes deafness associated with progressive degeneration of cochlear stereocilia. Journal of Cell Biology 166: 559-570. PubMed ID: 15314067
- Lee K, Amin Ud Din M, Ansar M, Santos-Cortez RL, Ahmad W, Leal SM. 2011. Autosomal recessive nonsyndromic hearing Impairment due to a novel deletion in the RDX gene. Genetics Research International 2011: 294675. PubMed ID: 22567349
- Miyagawa M, Naito T, Nishio SY, Kamatani N, Usami S. 2013. Targeted exon sequencing successfully discovers rare causative genes and clarifies the molecular epidemiology of Japanese deafness patients. PLoS One 8: e71381. PubMed ID: 23967202
- Pataky F, Pironkova R, Hudspeth AJ. 2004. Radixin is a constituent of stereocilia in hair cells. Proceedings of the National Academy of Sciences USA 101: 2601-2606. PubMed ID: 14983055
- Shearer AE, Hildebrand MS, Bromhead CJ, Kahrizi K, Webster JA, Azadeh B, Kimberling WJ, Anousheh A, Nazeri A, Stephan D, Najmabadi H, Smith RJH, Bahlo M. 2009. A novel splice site mutation in the RDX gene causes DFNB24 hearing loss in an Iranian family. American Journal of Medical Genetics 149A: 555-558. PubMed ID: 19215054
- Wilgenbus KK, Milatovich A, Francke U, Furthmayr H. 1993. Molecular cloning, cDNA sequence, and chromosomal assignment of the human radixin gene and two dispersed pseudogenes. Genomics 16: 199–206. PubMed ID: 8486357
Ordering/Specimens
Ordering Options
We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.
myPrevent - Online Ordering
- The test can be added to your online orders in the Summary and Pricing section.
- Once the test has been added log in to myPrevent to fill out an online requisition form.
- PGnome sequencing panels can be ordered via the myPrevent portal only at this time.
Requisition Form
- A completed requisition form must accompany all specimens.
- Billing information along with specimen and shipping instructions are within the requisition form.
- All testing must be ordered by a qualified healthcare provider.
For Requisition Forms, visit our Forms page
If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.
Specimen Types
Specimen Requirements and Shipping Details
PGxome (Exome) Sequencing Panel
PGnome (Genome) Sequencing Panel
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ORDER OPTIONS
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2) Select Additional Test Options
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