Karelian Bear Dog — Progressive rod-cone degeneration, PRCD-related (hereditary; OMIA-verified breed predisposition)

--- license: permission_granted topic_id: companion_breed_health_karelian_bear_dog_omia2489_dog category: companion-breed-health title: "Karelian Bear Dog — Progressive rod-cone degeneration, PRCD-related (hereditary; OMIA-verified breed predisposition)" lang: en source: "OMIA (Online Mendelian Inheritance in Animals, University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; C1 substring-verified. Pulled 2026-08-02 from local OMIA database dump." source_file: pdf-raw/breed-health/karelian_bear_dog_omia2489_2489.txt date_parsed: 2026-08-02 tokens_estimated: 1016 verification: method: substring_match claims: 7 passed: 7 date: 2026-08-02 recovered: false path: companion-breed-health/companion_breed_health_karelian_bear_dog_omia2489_dog/01_companion_breed_health_karelian_bear_dog_omia2489_dog.md source_document: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" citation: authority: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" title: "Karelian Bear Dog — Progressive rod-cone degeneration, PRCD-related (hereditary; OMIA-verified breed predisposition)" url: "https://omia.org/OMIA001298/9615/" retrieved: "2026-08-02" ref: "OMIA breed-specific hereditary-disorder records (omia.org), derived from local OMIA database dump; dataset: https://doi.org/10.25910/2AMR-PV70" doc_type: "academic animal-genetics database (breed-specific disorder entries)" needs_review: false

Karelian Bear Dog — Progressive rod-cone degeneration, PRCD-related (hereditary; OMIA-verified breed predisposition)

Source: first-hand OMIA (University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; every claim below is a C1 byte-substring of it.

Claims

Breed: Karelian Bear Dog (Dog)
Disorder:
Mode of inheritance: Autosomal recessive
Clin feat: 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]
Defect: yes
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.5Ggt;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.5Ggt;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) Ggt;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.

Associated gene(s)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

Gene: Entrez Gene ID 28634284 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
OMIA molecular-genetics note: 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".

Evidence (references)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

1990. Segregation distortion in inheritance of progressive rod cone degeneration (Prcd) in Miniature Poodle dogs. American Journal of Medical Genetics — PubMed:PMID2309782 | DOI:10.1002/ajmg.1320350309 — OMIA Phene_Article / Article
1996. Nonallelism of erd and prcd and exclusion of the canine rds peripherin gene as a candidate for both retinal degeneration loci. Investigative Ophthalmology & Visual Science — PubMed:PMID8603863 — OMIA Phene_Article / Article
1988. Variation in retinal degeneration phenotype inherited at the prcd locus. Experimental Eye Research — PubMed:PMID3164273 — OMIA Phene_Article / Article
1998. Linkage analysis and comparative mapping of canine progressive rod-cone degeneration (prcd) establishes potential locus homology with retinitis pigmentosa (RP17) in humans. Proceedings of the National Academy of Sciences of the United States of America — PubMed:PMID9501213 — OMIA Phene_Article / Article
1997. Cloning of canine ROM-1 and its investigation as a candidate gene for generalized progressive retinal atrophies in dogs. Animal Genetics — PubMed:PMID9589581 — OMIA Phene_Article / Article
1998. Researchers discover likely link between human, canine gene and blindness. Journal of the American Veterinary Medical Association — PubMed:PMID9634355 — OMIA Phene_Article / Article
1998. Identification of a RAPD marker linked to progressive rod-cone degeneration in dogs. Mammalian Genome — PubMed:PMID9716659 — OMIA Phene_Article / Article
1998. Isolation and investigation of canine phosducin as a candidate for canine generalized progressive retinal atrophies. Experimental Eye Research — PubMed:PMID9820795 | DOI:10.1006/exer.1998.0569 — OMIA Phene_Article / Article
1999. Evaluation of the APOH gene as a positional candidate for prcd in dogs. Investigative Ophthalmology & Visual Science — PubMed:PMID10235557 — OMIA Phene_Article / Article
2006. Identical mutation in a novel retinal gene causes progressive rod-cone degeneration in dogs and retinitis pigmentosa in humans. Genomics — PubMed:PMID16938425 | DOI:10.1016/j.ygeno.2006.07.007 — OMIA Phene_Article / Article
2009. Real-time detection of the mutation responsible for progressive rod-cone degeneration in Labrador Retriever dogs using locked nucleic acid TaqMan probes. J Vet Diagn Invest — PubMed:PMID19737766 — OMIA Phene_Article / Article
2006. Linkage disequilibrium mapping in domestic dog breeds narrows the progressive rod-cone degeneration interval and identifies ancestral disease-transmitting chromosome. Genomics — PubMed:PMID16859891 | DOI:10.1016/j.ygeno.2006.05.013 — OMIA Phene_Article / Article
(26 additional references in OMIA)

Comparative medicine (human OMIM)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

OMIM:610598 (type: gene) — OMIA Group_OMIM (via OMIA_ID)
OMIM:610599 (type: trait) — OMIA Group_OMIM (via OMIA_ID)

verification_derived: method: derived_from_dataset source: "OMIA database dump (omia.xml, local); fields Gene/Variant/Article/OMIM" note: "Structured fields (gene, variant rsID/protein change, PubMed/DOI references, OMIM cross-link) extracted from OMIA dump and presented with first-hand values; not verbatim prose."

Karelian Bear Dog — Progressive rod-cone degeneration, PRCD-related (hereditary; OMIA-verified breed predisposition)