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Cone-Rod Dystrophy and Retinitis Pigmentosa via the CFAP418/C8orf37 Gene

Summary and Pricing

Test Method

Sequencing and CNV Detection via NextGen Sequencing using PG-Select Capture Probes
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
15151 CFAP418 81479 81479,81479 $990 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
15151CFAP41881479 81479,81479 $990 Order Options and Pricing

Pricing Comments

This test is also offered via our exome backbone with CNV detection (click here). The exome-based test may be higher priced, but permits reflex to the entire exome or to any other set of clinically relevant genes.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Testing run on PG-Select capture probes does not include exome-wide CNV analysis. Reflex is available to PGxome or an exome-based panel, or you can use this gene list to create a custom panel (click here).

Click here for costs to reflex to whole PGxome.

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.

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Dana Talsness, PhD

Clinical Features and Genetics

Clinical Features

Cone rod dystrophies (CORDs/CRDs) are characterized by dysfunction or degeneration of cone photoreceptors with relative preservation of rod function in the initial stages. The most common symptoms are photophobia and epiphora in bright light, decreased visual acuity, and dyschromatopsia. Fundus changes may vary from mild pigment granularity to a distinct atrophic lesion in the central macula. As the disease progresses, degeneration of rod photoreceptors also occurs and leads to progressive night blindness and peripheral visual field loss. Cone rod dystrophies (1/40,000) are 10 times less common than RP (Hamel. 2007). Retinitis pigmentosa (RP) represents a group of hereditary retinal dystrophies with a worldwide prevalence of ~1 in 4000 (Booij et al. 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. 1999).

Genetics

Genes that are associated with both autosomal recessive (ar) CRD and RP encode proteins that are involved in phototransduction, retinoid metabolism, transport through connecting cilium, cell-to-cell signaling or synaptic interaction (Estrada-Cuzcano et al. 2012). Mutations in CFAP418/C8orf37 can lead to an early or adolescent-onset arCRD or arRP phenotype with early macular atrophy. Postaxial polydactyly has been reported in one family, which suggests a syndromic phenotype (van Huet et al. 2013). CFAP418 encoded polypeptide function is unknown because it lacks known functional protein domains. CFAP418 is expressed ubiquitously. High mRNA expression levels were found in brain, heart, and retina. Immunohistochemical studies revealed that CFAP418 localization at the base of the photoreceptor connecting cilia (Estrada-Cuzcano et al. 2012). Immunolocalization study, and the presence of postaxial polydactyly in one of the families who had CFAP418 mutations suggested a plausible ciliary function of the CFAP418 encoded polypeptide (Estrada-Cuzcano et al. 2012; van Huet et al. 2013). These studies also suggest that CFAP418 may be implicated in Bardet-Biedl syndrome or in other ciliopathies. Only a few causative mutations have been reported in CFAP418. These are missense, nonsense and splicing (Human Gene Mutation Database). CFAP418 mutation analysis in 4 unrelated consanguineous families with retinal dystrophies identified homozygous CFAP418 mutations in all affected individuals (Estrada-Cuzcano et al. 2012).

Clinical Sensitivity - Sequencing with CNV PG-Select

Predicting clinical sensitivity for the CFAP418 gene is challenging due to genetic heterogeneity of both cone rod dystrophy and retinitis pigmentosa and also due to the limited number of documented cases. However, analytical sensitivity is expected to be high because all mutations reported are detectable by this method (Human Gene Mutation Database).

Testing Strategy

This test is performed using Next-Generation sequencing with additional Sanger sequencing as necessary.

This test provides full coverage of all coding exons of the CFAP418 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.

Indications for Test

All patients with symptoms suggestive of Cone-rod dystrophy. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in CFAP418.

Gene

Official Gene Symbol OMIM ID
CFAP418 614477
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Cone-rod dystrophy 16 AR 614500

Citations

  • Booij JC. et al. 2005. Journal of medical genetics. 42: e67. PubMed ID: 16272259
  • Estrada-Cuzcano A, Neveling K, Kohl S, Banin E, Rotenstreich Y, Sharon D, Falik-Zaccai TC, Hipp S, Roepman R, Wissinger B, Letteboer SJF, Mans DA, et al. 2012. Mutations in C8orf37, Encoding a Ciliary Protein, are Associated with Autosomal-Recessive Retinal Dystrophies with Early Macular Involvement. The American Journal of Human Genetics 90: 102109. PubMed ID: 22177090
  • Hamel CP. 2007. Cone rod dystrophies. Orphanet J Rare Dis 1;2:7. PubMed ID: 17270046
  • Human Gene Mutation Database (Bio-base).
  • van Huet RA, Estrada-Cuzcano A, Banin E, Rotenstreich Y, Hipp S, Kohl S, Hoyng CB, Hollander AI den, Collin RW, Klevering BJ. 2013. Clinical characteristics of rod and cone photoreceptor dystrophies in patients with mutations in the C8orf37 gene. Investigative ophthalmology & visual science 54: 46834690. PubMed ID: 23788369
  • Van Soest S., Westerveld A. 1999. Survey of ophthalmology. 43: 321-34. PubMed ID: 10025514

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

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ORDER OPTIONS

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STAT and Prenatal Test Options are not available with Patient Plus.

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
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