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Autosomal Dominant Retinitis Pigmentosa 17 (RP17) via the CA4 Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
CA4 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8521CA481479 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.


Genetic Counselors


  • Dana Talsness, PhD

Clinical Features and Genetics

Clinical Features

Retinitis pigmentosa (RP; OMIM # 268000) represents a group of hereditary retinal dystrophies with a worldwide prevalence of ~1 in 4000 (Booij et al. J Med Genet 42 (11): e67, 2005). RP is clinically characterized by retinal pigment deposits visible on fundus examination, nyctalopia ("night blindness"), followed by progressive degeneration of the photoreceptors, which eventually leads to blindness (van Soest et al. Surv Ophthalmol 43(4):321-334, 1999). RP17 (OMIM # 600852) is characterized by the reduction of both rod (scotopic) and cone (photopic and flicker) responses in the electroretinogram (Yang et al. Hum Mol Genet 14(2):255-265, 2005).


Nonsyndromic RP is remarkably heterogeneous both clinically and genetically and exhibits autosomal dominant (ad), autosomal recessive (ar) or X-linked (XL) inheritance. To date, over 50 loci have been linked to nonsyndromic RP and 18, 27 and 2 genes have been identified that are associated with adRP, arRP, and XLRP, respectively (RetNet). Carbonic anhydrase 4 (CA4; OMIM # 114760), the adRP gene located on 17q23.1 encodes a glycosylphosphatidylinositol membrane-anchored zinc metalloenzyme (the CAIV protein), which is predominantly expressed in the choriocapillaris of the eye, but not in the retina (Alvarez et al. Invest Ophthalmol Vis Sci 48(8):3459-3468, 2007; Rebello et al. Proc Natl Acad Sci U S A 101(17):6617-6622, 2004; Yang et al., 2005). Retinal phototransduction is highly sensitive to extracellular pH changes. pH homeostasis is maintained by efficient acid removal mediated by choriocapillaris from the retina and retinal pigment epithelium (RPE), which have a high rate of metabolism and consequently a high rate of endogenous acid production. This process requires the functional interaction between CAIV and Na+/bicarbonate co-transporter 1 (NBC1). The CAIV and NBC1 complex is specifically expressed in the choriocapillaris (Alvarez et al. Biochemistry 42(42):12321-9, 2003). So far, about 10 mutations (missense and regulatory variants) in CA4 have been associated with adRP (Human Gene Mutation Database), and these pathogenic mutations have been shown to impair the CAIV and NBC1 interaction. Also, functional analysis of two CA4 mutations (Arg14Trp, Arg219Ser) revealed that they lead to the accumulation of unfolded forms of CAIV in the endoplasmic reticulum (ER) of choriocapillaris endothelial cells, which subsequently activates the unfolded protein response (UPR). The induced UPR leads to chronic ER stress and ultimately apoptosis of these cells and subsequently leads to ischemia of the overlying retina and adRP (Rebello et al., 2004).

Clinical Sensitivity - Sequencing with CNV PGxome

Mutational screening in 96 patients with simplex RP and adRP of Chinese ethnicity, identified a CA4 pathogenic mutation (R69H) in 1 patient with simplex RP (~1%), which was not found in 432 normal chromosomes (Alvarez et al. Invest Ophthalmol Vis Sci 48(8):3459-3468, 2007).

So far, no gross deletions or duplications have been reported in CA4 (Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the CA4 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

All patients with symptoms suggestive of adRP, specifically patients with symptoms suggestive of RP17 described in the clinical features section.


Official Gene Symbol OMIM ID
CA4 114760
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Retinitis Pigmentosa 17 AD 600852

Related Test

Retinitis Pigmentosa Panel


  • Alvarez, B.V. et al. (2003). "Direct extracellular interaction between carbonic anhydrase IV and the human NBC1 sodium/bicarbonate co-transporter." Biochemistry 42(42):12321-12329. PubMed ID: 14567693
  • Alvarez, B.V. et al. (2007).  "Identification and characterization of a novel mutation in the carbonic anhydrase IV gene that causes retinitis pigmentosa." Invest Ophthalmol Vis Sci 48(8):3459-3468. PubMed ID: 17652713
  • Booij JC. 2005. Identification of mutations in the AIPL1, CRB1, GUCY2D, RPE65, and RPGRIP1 genes in patients with juvenile retinitis pigmentosa. Journal of Medical Genetics 42: e67–e67. PubMed ID: 16272259
  • Human Gene Mutation Database (Bio-base).
  • Rebello, G. et al. (2004). "Apoptosis-inducing signal sequence mutation in carbonic anhydrase IV identified in patients with the RP17 form of retinitis pigmentosa." Proc Natl Acad Sci USA 101(17):6617-6622. PubMed ID: 15090652
  • RetNet
  • Van Soest S., Westerveld A. 1999. Survey of ophthalmology. 43: 321-34. PubMed ID: 10025514
  • Yang, Z. et al. (2005). "Mutant carbonic anhydrase 4 impairs pH regulation and causes retinal photoreceptor degeneration." Hum Mol Genet 14(2):255-265. PubMed ID: 15563508


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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