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Retinitis Pigmentosa via the IMPDH1 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
IMPDH1 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8221IMPDH181479 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

Nonsyndromic retinitis pigmentosa (RP, OMIM 268000) is a large group of inherited degenerative diseases of the retina characterized by abnormalities of the photoreceptors or the retinal pigment epithelium. It is a progressive disease. Symptoms usually begin with night blindness, progressing to constriction of the peripheral visual field and, eventually, loss of central vision. The age of onset varies from childhood to middle age (Gu et al. J Med Genet 36:705-707, 1999). The clinical hallmarks are an abnormal fundus with bone-spicule deposits and attenuated retinal vessels, abnormal electroretinographic findings and reduced visual fields (Daiger et al. Arch Ophthalmol 125:151-158, 2007). RP affects 1 in 3,000 people worldwide (Farrar et al. EMBO J 21:857-864, 2002). Genetic abnormalities are the primary cause of RP.


Retinitis pigmentosa (RP) is genetically and clinically heterogeneous (Koenekoop et al. Clin Experiment Ophthalmol 35:473-485, 2007). At least four distinct subgroups are recognized on the basis of the mode of inheritance and age of onset. These include autosomal dominant-RP (AD-RP), autosomal recessive (AR-RP), X-linked, and digenic (Rivolta et al. Hum Mol Genet 11:1219-1227, 2002; Kajiwara et al. Science 264:1604-1608, 1994). In addition, RP can be inherited as a mitochondrial trait (Mansergh et al. Am J Hum Genet 64:971-985, 1999). Genetic heterogeneity is documented within each subgroup. About 50% of patients with RP are isolated cases with no known affected relatives. It is unclear how many of these are real isolated cases caused by de novo variants or inherited with low penetrance. AD-RP affects all ethnic groups, although variants in particular genes have been identified in specific populations. Patients with AD-RP represent 15-25% of all cases (Fishman Arch Ophthalmol 96:822-826, 1978). Currently, variants in 18 genes account for at least 58% of AD-RP cases. These include the IMPDH1 gene. At least 8 different IMPDH1 variants have been reported in patients with AD-RP. The most common disease-causing variant, Asp226Asn, accounts for at ~ 1% of all cases of AD-RP (Bowne et al. Invest Ophthalmol Vis Sci 47:34-42, 2006). Notably, the variant Arg231Pro was associated with a severe form of AD-RP in one family in which all patients presented with early-onset, severe loss of visual acuity and nondetectable ERG signals (Groveret al. Ophthalmology 111:1910-1916, 2004). These observations led the authors to suggest that patients with a severe form of AD-RP should be investigated for variants in the IMPDH1 gene. In addition to AD-RP, heterozygous variants in the IMPDH1 gene were found in isolated cases of Leber congenital amaurosis (LCA, OMIM 146690; Bowne et al. 2006).

The IMPDH1 gene encodes the inosine monophosphate dehydrogenase type1 enzyme, which catalyzes the rate-limiting step of de novo guanine nucleotide biosynthesis.

Clinical Sensitivity - Sequencing with CNV PGxome

This test allows the detection of variants in approximately 2.8 % of patients with AD-RP (Daiger Adv Exp Med Bio 613:203-209, 2008) and rare isolated cases of LCA.

Testing Strategy

This test provides full coverage of all coding exons of the IMPDH1 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 AD-RP or sporadic RP. The IMPDH1 gene may also be a candidate for patients with LCA with no variants detected in the commonly mutated genes.


Official Gene Symbol OMIM ID
IMPDH1 146690
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Related Tests

Leber Congenital Amaurosis Panel
Retinitis Pigmentosa Panel


  • Bowne, S. J., et.al. (2006). "Spectrum and frequency of mutations in IMPDH1 associated with autosomal dominant retinitis pigmentosa and leber congenital amaurosis." Invest Ophthalmol Vis Sci 47(1): 34-42. PubMed ID: 16384941
  • Daiger et al. 2007. PubMed ID: 17296890
  • Daiger, S. P., et.al. (2008). "Mutations in known genes account for 58% of autosomal dominant retinitis pigmentosa (adRP)." Adv Exp Med Biol 613: 203-9. PubMed ID: 18188946
  • Farrar, G. J., et.al. (2002). "On the genetics of retinitis pigmentosa and on mutation-independent approaches to therapeutic intervention." Embo J 21(5): 857-64. PubMed ID: 11867514
  • Fishman, G. A. (1978). "Retinitis pigmentosa. Genetic percentages." Arch Ophthalmol 96(5): 822-6. PubMed ID: 655919
  • Grover, S., et.al. (2004). "A novel IMPDH1 mutation (Arg231Pro) in a family with a severe form of autosomal dominant retinitis pigmentosa." Ophthalmology 111(10): 1910-6. PubMed ID: 15465556
  • Gu S. et al. 1999. Journal of Medical Genetics. 36: 705-7. PubMed ID: 10507729
  • Kajiwara, K. et.al. (1994). "Digenic retinitis pigmentosa due to mutations at the unlinked peripherin/RDS and ROM1 loci." Science 264(5165): 1604-1608. PubMed ID: 8202715
  • Koenekoop, R. K., et.al. (2007). "Genetic testing for retinal dystrophies and dysfunctions: benefits, dilemmas and solutions." Clin Experiment Ophthalmol 35(5): 473-85. PubMed ID: 17651254
  • Mansergh, F. C., et.al. (1999). "Retinitis pigmentosa and progressive sensorineural hearing loss caused by a C12258A mutation in the mitochondrial MTTS2 gene." Am J Hum Genet 64(4): 971-85. PubMed ID: 10090882
  • Rivolta, C., et.al. (2002). "Retinitis pigmentosa and allied diseases: numerous diseases, genes, and inheritance patterns." Hum Mol Genet 11(10): 1219-27. PubMed ID: 12015282


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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