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Canine Mendelian disease record

Progressive Rod-Cone Degeneration (prcd-PRA)

Progressive Rod-Cone Degeneration (prcd-PRA). Autosomal recessive. Observed in 79 of 266 breeds tested in the Sniff Atlas, with measured carrier frequencies drawn from 242,217 dogs (Donner 2023). Per-dog phenotype outcome depends on penetrance, modifiers, and environment; the carrier frequencies below describe variant prevalence, not disease incidence.

OMIA identifier
OMIA:001298-9615
Autosomal recessive
Source dataset
Sniff Atlas v1.0.1 / DOI
The human connection

A model of human retinitis pigmentosa 36

This is the canine counterpart of retinitis pigmentosa 36 in people. That makes affected dogs a naturally-occurring model of the human disease, and it is part of why studying dogs moves medicine forward for everyone. It does not mean your dog has the human disease. It means the two share an underlying biology.

In people, the disease is described as: Any retinitis pigmentosa in which the cause of the disease is a mutation in the PRCD gene.

In humans it is also called: RP36, PRCD retinitis pigmentosa, retinitis pigmentosa caused by mutation in PRCD, retinitis pigmentosa type 36, RP 36.

MONDO:0012523 OMIM 610599

Mapped from OMIA via the human disease's OMIM entry to the Mondo Disease Ontology (Monarch Initiative, CC-BY 4.0). Sniff renders this as a model-of link; the canine disease remains the subject of this page.

About this disease

From OMIA's curated record

Documented in OMIA (Online Mendelian Inheritance in Animals). This describes the disease as recorded in the published literature, not a prediction for any individual dog. As of 2026-06-03.

Summary

This disorder has been renamed in OMIA on the basis of the review by Miyadera et al. (2012). The name was updated to include 'PRCD-related' [12/06/2024]

Clinical features

Clinical features of the disease are a result of degeneration of the rods and cones in the eye (Spencer et al., 2016). Dogs are born with normal vision but in adolescence or early adulthood begin to show clinical signs (Miyadera, 2014). The disease typically manifests initially as a lack of coordination in dim light and night blindness (Miyadera, 2014). Affected dogs may also show an aversion to bright lights, difficulty navigating familiar areas and failure to focus on small objects such as balls or toys (Miyadera, 2014). As the cones of the eye degenerate, the night blindness will progress to day blindness (Miyadera, 2012). Ultimately, the disease results in total blindness (Miaydera, 2012). Currently, there is no known cure or treatment for slowing down progression of PRCD. Progression varies between individuals but most dogs become completely blind in 1 – 2 years (Zangerl et al., 2006). [IT thanks DVM student Lauren Alam, who provided the basis of this contribution in April 2022]

Molecular genetics

Zangerl et al. (2006) identified a novel gene that they called PRCD in a 106kb candidate region on CFA9. They also showed that "a homozygous mutation (TGC>TAC) in the second codon shows complete concordance with the disorder in 18 different dog breeds/breed varieties tested".

Pathology

The PRCD protein is bound to discs in the outer segments of rods and cones (Spencer et al., 2016; Allon et al., 2019). The PRCD protein is essential for long-term photoreceptor viability (Spencer et al., 2019). In PRCD disease, the protein is mislocalised from the outer segment discs (Spencer et al., 2016). In early disease about 40% reduction in rod disc renewal is seen, and the visual cells of the posterior pole and equatorial regions of the eye demonstrate vesicular appearances and outer segment lamellar disorientation (Aguirre et al., 1982; Spencer et al., 2019). As the disease progresses, all photoreceptor outer segments display changes including misoriented discs, subretinal invasion of phagocytic cells and extracellular vesicles (Spencer et al., 2019). Outer segments are eventually lost entirely (Spencer et al., 2019). [IT thanks DVM student Lauren Alam, who provided the basis of this contribution in April 2022]

Prevalence

Lewis and Mellersh (2019) reported a decline in frequency of the PRCD:c.5G>A variant in Labrador Retrievers from 0.078 (7.8%) prior to publication of the variant, to 0.003 (0.3%) 8-10 years after publication of the variant. This represents a 96.5% decline in frequency of the variant as a result of testing. For the same variant in English Cocker Spaniels, the equivalent results were a decline in frequency from 0.126 (12.6%) to 0.006 (0.6%) 8-10 years after publication of the variant, which represents a decline in frequency of 95.1% as a result of testing. Andrade et al. (2019) reported the frequency of this same variant in English Cocker Spaniels in Brazil: "220 ECS dogs was used for genotyping, of which 131 were registered from 18 different kennels and 89 were unregistered. . . . The . . .[PRCD:c.5G>A] allele frequency was 25.5%. Among the registered dogs, the allele frequency was 14.9%; among the dogs with no history of registration, the allele frequency was 41%." Clark et al. (2023) "utilized a large set of genotypes from dogs tested for the progressive rod-cone degeneration–progressive retinal atrophy (prcd-PRA) G>A missense PRCD variant (n = 86,667) and the collie eye anomaly (CEA)-associated NHEJ1 deletion (n = 33,834) ... . ... Forty-one breeds and breed mixes in our prcd-PRA dataset were genotyped for having at least one copy of the PRCD variant ... . Regression modeling showed time progression to significantly affect the odds of a dog being homozygous or heterozygous for either disease, as do variables including breed and breed popularity. This study shows that genetic testing informed breeding decisions to produce fewer affected dogs. However, the presence of dogs homozygous for the disease variant, especially for prcd-PRA, was still observed fourteen years after test availability, potentially due to crosses of unknown carriers."

Human analog

OMIA links this condition to its human counterpart in OMIM (Mendelian Inheritance in Man), the place to read across to the deeper human literature for the same biology.

Disease · OMIM 610599 Gene · OMIM 610598

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:001298-9615, doi:10.25910/2AMR-PV70 (CC-BY 4.0).

The evidence

Published references

The peer-reviewed papers behind this disease, curated by OMIA. Starred entries are OMIA-designated landmark papers. Showing 6 of 38.

  1. Development of cost-effective PCR-RFLP methods for screening Mendelian disorders in Chihuahua dogs. · F.U. Vet. J. Health Sci. · 2026
  2. PRCD-associated retinitis pigmentosa in dogs and humans. · Exp Eye Res · 2026 · PMID 42107853

References curated by OMIA (Nicholas, Tammen & the Sydney Informatics Hub), doi:10.25910/2AMR-PV70 (CC-BY 4.0). Full list at the OMIA entry.

Predict a litter

Set each parent's status for Progressive Rod-Cone Degeneration (prcd-PRA) and see the odds for their puppies. Single recessive variant, exact Mendelian math.

Parent A
Parent B
NNClear
NmCarrier
NmCarrier
mmAffected
Clear25%
Carrier50%
Affected25%

These are the genetic odds for one known variant, not a promise: a real litter varies around them, and penetrance or other genes can change whether the condition ever appears. Use it to avoid pairing two carriers and to keep a line healthy, not to engineer a dog. Inheritance mode per OMIA.
Your breed

See what Progressive Rod-Cone Degeneration (prcd-PRA) looks like in your dog's breed.
Carrier frequency by breed

Top 25 well-sampled breeds (n ≥ 50)

Maximum per breed across variants in the Donner 2023 cohort, with . The list below is split into well-sampled breeds (n ≥ 50 tested) and small-sample breeds (n < 50, where the Wilson CI typically spans more than 20 percentage points and frequencies should not be compared directly to the well-sampled entries). Frequencies are population-level, not per-litter or per-line.

0%25%50%
Australian Cattle Dog30.7% · n 980
Karelian Bear Dog25.7% · n 68
American Eskimo Dog16.9% · n 301
Schnauzer Giant13.1% · n 229
Cocker Spaniel13.0% · n 1,879
Nova Scotia Duck Tolling Retriever11.1% · n 63
Miniature American Shepherd9.8% · n 1,474
Chesapeake Bay Retriever9.6% · n 136
English Cocker Spaniel9.5% · n 579
Finnish Lapphund8.8% · n 57
Spanish Water Dog8.3% · n 96
Poodle Miniature8.2% · n 3,547
Portuguese Water Dog7.8% · n 663
Labrador Retriever7.2% · n 16,825
Yorkshire Terrier6.8% · n 8,343
n = 35,240 dogs · Donner et al. 2023 carrier-screening cohort · Sniff Atlas
Each bar is one well-sampled breed; the whisker is its Wilson 95% CI, and fainter bars have wider intervals. Frequencies are population-level, not per-litter. Carrier status for Progressive Rod-Cone Degeneration (prcd-PRA) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Carrier frequency n tested
Australian Cattle Dog 30.7% 980
Karelian Bear Dog 25.7% 68
American Eskimo Dog 16.9% 301
Schnauzer Giant 13.1% 229
Cocker Spaniel 13.0% 1,879
Nova Scotia Duck Tolling Retriever 11.1% 63
Miniature American Shepherd 9.8% 1,474
Chesapeake Bay Retriever 9.6% 136
English Cocker Spaniel 9.5% 579
Finnish Lapphund 8.8% 57
Spanish Water Dog 8.3% 96
Poodle Miniature 8.2% 3,547
Portuguese Water Dog 7.8% 663
Labrador Retriever 7.2% 16,825
Yorkshire Terrier 6.8% 8,343
Coton De Tulear 5.3% 104
Barbet 4.7% 106
Chinese Crested 2.9% 204
Golden Retriever 2.7% 12,860
Dalmatian 2.4% 816
Poodle Toy 2.1% 94
Tibetan Terrier 2.1% 95
Pomeranian 2.1% 5,285
Biewer Terrier 1.9% 184
Bichon Frise 1.1% 1,066

Top 25 of 65 well-sampled breeds with at least one observed carrier shown.

▸ Also observed in 14 small-sample breeds (n < 50)

Frequencies in this section are statistical estimates with wide Wilson 95% confidence intervals (typically >20 percentage points). Treat these as "carriers observed but the true population frequency is not yet measurable" rather than as comparable to the well-sampled entries above.

Breed Estimate n tested
Kuvasz 14.3% 7
Kai Ken 11.1% 9
Lapponian Herder 9.6% 26
Lancashire Heeler 8.8% 17
Nordic Spitz 8.3% 6
Field Spaniel 6.9% 29
Russian Tsvetnaya Bolonka 6.7% 15
Rat Terrier 6.3% 8
Entlebucher Mountain Dog 4.5% 11
Manchester Terrier Toy 4.2% 12
Puli 4.2% 12
Plott 4.0% 25
Portuguese Podengo Pequenos 2.9% 17
Black Russian Terrier 2.2% 23

187 additional breeds in the Donner 2023 cohort were tested but showed no carriers.

Scope of this record

Scope

This record carries the breed-level carrier frequencies from the Donner 2023 cohort. Penetrance data (the fraction of at-risk dogs that develop the phenotype) is not yet quantified for this disease in the Sniff Atlas v1.0.1. The OMIA entry is the authoritative reference for the clinical phenotype, inheritance pattern, and gene assignment.

Predicted disease relevance at the per-dog level is UNPROVEN. The carrier frequency is measured; phenotype outcome depends on penetrance, environment, and modifier loci. Consult a veterinarian for clinical interpretation.

How to cite this record

Citations

If you use this record in published work, cite the Sniff Atlas (the published dataset that carries the breed-level carrier frequencies) and the upstream sources:

  • Sniff Atlas v1.0.1 for the per-breed carrier frequencies:

    Gehring, M. (2026). Sniff Atlas v1.0.1. Zenodo. https://doi.org/10.5281/zenodo.20566358. CC-BY 4.0.

  • OMIA for the disease definition, inheritance, and gene assignment:

    Nicholas, F. W., & Tammen, I. (2024). OMIA. Sydney Informatics Hub, The University of Sydney. https://doi.org/10.25910/2AMR-PV70. Entry: OMIA:001298-9615.

  • Donner et al. 2023 for the breed × variant carrier-frequency cohort:

    Donner, J., Freyer, J., Davison, S., Anderson, H., Blades, M., Honkanen, L., et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics, 19(2), e1010651. https://doi.org/10.1371/journal.pgen.1010651.

Full citation formats (BibTeX, RIS, CITATION.cff) at sniff.world/cite.

Related

Related

Last updated
Sources: Sniff Atlas v1.0.1 · OMIA OMIA:001298-9615 · Donner et al. 2023