Bietti Crystalline Corneoretinal Dystrophy via the CYP4V2 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 | |
|---|---|---|---|---|---|
| 8235 | CYP4V2 | 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
Bietti crystalline corneoretinal dystrophy (BCD) is an autosomal recessive chorioretinal degeneration disorder. It is characterized by the presence of yellow-white crystals in the corneal limbus and the retina associated with progressive atrophy of the retinal pigment epithelium (RPE) and sclerosis of choroidal vessels. In some patients, these crystalline deposits are also present in circulating lymphocytes (Wilson et al. 1989). Symptoms include decreased visual acuity, nyctalopia and paracentral scotomas. Later, patients develop constriction of the visual fields and slowly marked visual impairment, which leads to legal blindness in the late stages (Okialda et al. 2012). BCD is a relatively rare disorder, but may be underdiagnosed (Okialda et al. 1993) with highest prevalence reported in East Asian populations, especially in China and Japan (Hu 1987).
Genetics
BCD is a clinically and genetically homogeneous disorder with autosomal recessive inheritance (Xiao et al. 2011). CYP4V2, which encodes a CYP450 family protein, is the only causative gene for this disease. CYP4V2 is widely expressed in several tissues including the retina, and RPE and has been reported to be responsible for the prevention of lipotoxicity (Li et al. 2004; Lai et al. 2010). Biochemical studies suggest that BCD is associated with abnormal lipid metabolism in binding, elongation, or desaturation, and results in crystalline deposits in retinas (Lee et al. 2001; Lai et al. 2010). There are ~50 sequence variations (missense, nonsense, splicing, small insertions and deletions) in CYP4V2 which have been associated with BCD (Li et al. 2004; The Human Gene Mutation Database).
Clinical Sensitivity - Sequencing with CNV PGxome
A mutation screen in the Chinese population identified pathogenic variations in CYP4V2 in all 21 families with Bietti crystalline corneoretinal dystrophy (BCD) (Xiao et al. 2011). Another study identified CYP4V2 mutations in eight (8/8) unrelated families and 9 (9/10) isolated individuals with BCD (Shan et al. 2005).
Testing Strategy
This test provides full coverage of all coding exons of the CYP4V2 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
Candidates for this test are patients with symptoms consistent of Bietti crystalline corneoretinal dystrophy, family members of patients who have known mutations and carrier testing for at-risk family members.
Candidates for this test are patients with symptoms consistent of Bietti crystalline corneoretinal dystrophy, family members of patients who have known mutations and carrier testing for at-risk family members.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| CYP4V2 | 608614 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Bietti Crystalline Corneoretinal Dystrophy | AR | 210370 |
Citations
- Hu DN. 1987. Prevalence and mode of inheritance of major genetic eye diseases in China. Journal of medical genetics 24: 584–588. PubMed ID: 3500313
- Human Gene Mutation Database (Bio-base).
- Lai TYY, Chu K-O, Chan K-P, Ng T-K, Yam GHF, Lam DSC, Pang C-P. 2010. Alterations in Serum Fatty Acid Concentrations and Desaturase Activities in Bietti Crystalline Dystrophy Unaffected by CYP4V2 Genotypes. Investigative Ophthalmology & Visual Science 51: 1092–1097. PubMed ID: 19797200
- Lee J, Jiao X, Hejtmancik JF, Kaiser-Kupfer M, Gahl WA, Markello TC, Guo J, Chader GJ. 2001. The metabolism of fatty acids in human Bietti crystalline dystrophy. Investigative ophthalmology & visual science 42: 1707–1714. PubMed ID: 11431432
- Li A, Jiao X, Munier FL, Schorderet DF, Yao W, Iwata F, Hayakawa M, Kanai A, Shy Chen M, Alan Lewis R. 2004. Bietti Crystalline Corneoretinal Dystrophy Is Caused by Mutations in the Novel Gene CYP4V2. The American Journal of Human Genetics 74: 817–826. PubMed ID: 15042513
- Okialda KA, Stover NB, Weleber RG, Kelly EJ. 2012. Bietti Crystalline Dystrophy. In: Pagon RA, Adam MP, Bird TD, Dolan CR, Fong C-T, and Stephens K, editors. GeneReviews™, Seattle (WA): University of Washington, Seattle. PubMed ID: 22497028
- Shan M, Dong B, Zhao X, Wang J, Li G, Yang Y, Li Y. 2005. Novel mutations in the CYP4V2 gene associated with Bietti crystalline corneoretinal dystrophy. Mol Vis 11: 738–743. PubMed ID: 16179904
- Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR. 1989. Bietti’s crystalline dystrophy. A clinicopathologic correlative study. Arch. Ophthalmol. 107: 213–221. PubMed ID: 2783846
- Xiao X, Mai G, Li S, Guo X, Zhang Q. 2011. Identification of CYP4V2 mutation in 21 families and overview of mutation spectrum in Bietti crystalline corneoretinal dystrophy. Biochem. Biophys. Res. Commun. 409: 181–186. PubMed ID: 21565171
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
No Additional Test Options are available for this test.