Progressive Retinal Atrophy, Cone-Rod Dystrophy 1 (American Staffordshire Terrier Type)
Affected Genes: PDE6B
Inheritance: Autosomal Recessive
Variant(canFam6):
chr3:94213190: G>T
Breed: American Bully
American Pit Bull Terrier
American Staffordshire Terrier
General Information: Progressive Retinal Atrophy, Cone-Rod Dystrophy 1 (PRA-crd1) in American Staffordshire Terriers manifests as a severe and progressive deterioration of the retina, starting as early as 11 weeks of age. This condition initially presents with signs of retinal thinning detectable via veterinary examinations between 3 to 6 months. As the disease advances, affected dogs experience significant vision impairment, usually becoming functionally blind by the time they reach one year of age. By 20 months, the retinal degeneration is often so severe that it results in complete blindness, profoundly affecting the dog’s ability to navigate their environment.
How to Read Your Dog's Test Results for this Genetic Variant:
Two Variants Detected: Dog Likely Affected
One Variant Detected: Dog Unlikely Affected
No Variants Detected: No Effect
Gene / Testing Information: Genetic testing for the PDE6B gene is critical in identifying carriers of Progressive Retinal Atrophy, Cone-Rod Dystrophy 1 (PRA-crd1) among American Staffordshire Terriers. This condition follows an autosomal recessive inheritance pattern, meaning that a dog must inherit two copies of the mutated gene—one from each parent—to express the disease. Dogs with only one copy of the mutation do not show symptoms but can pass the gene to their offspring. When two carriers are bred, there is a 25% chance of producing affected offspring and a 50% likelihood that each puppy will be a carrier. Strategic genetic testing is essential to manage breeding practices effectively, aiming to reduce the prevalence of this debilitating disease. Breeders are strongly advised against mating two carriers to prevent the birth of affected puppies. Those dogs tested clear of the mutation do not increase the risk of propagating the condition, though it is crucial to note that a clear test for PDE6B does not rule out other forms of Progressive Retinal Atrophy due to different genetic mutations.
References:
Goldstein O, Mezey JG, Schweitzer PA, Boyko AR, Gao C, Bustamante CD, Jordan JA, Aguirre GD, Acland GM. IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Invest Ophthalmol Vis Sci. 2013 54(10):7005-7019.
Kijas JW, Zangerl B, Miller B, Nelson J, Kirkness EF, Aguirre GD, Acland GM. Cloning of the canine ABCA4 gene and evaluation in canine cone-rod dystrophies and progressive retinal atrophies. Mol Vis. 2004 10:223-232.