Progressive Retinal Atrophy, Cone-Rod Dystrophy 2 (American Staffordshire Terrier Type)
Affected Genes: IQCB1
Inheritance: Autosomal Recessive
Variant(canFam6):
chr33:25104412-25104413: 1 bp insertion G
Breed: American Bully
American Pit Bull Terrier
American Staffordshire Terrier
General Information: Progressive Retinal Atrophy, Cone-Rod Dystrophy 2 (PRA-crd2), is a severe genetic disorder affecting the American Staffordshire Terrier, characterized by early onset degeneration of the retina's photoreceptor cells. Symptoms typically manifest by 12 weeks of age with noticeable retinal thinning detectable upon veterinary examination by 3 to 6 months. Affected dogs experience a rapid decline in vision, becoming severely impaired by one year and advancing to complete blindness by approximately 20 months of age. This disorder profoundly impacts the quality of life, as affected dogs must adapt to progressive visual impairment.
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: The genetic testing for Progressive Retinal Atrophy, Cone-Rod Dystrophy 2 (PRA-crd2) targets the IQCB1 gene to determine whether American Staffordshire Terriers carry the genetic mutation responsible for this form of retinal degeneration. The condition is transmitted through an autosomal recessive pattern, meaning a dog must inherit two copies of the defective gene—one from each parent—to exhibit symptoms of the disease. Dogs with one copy of the mutation do not show clinical signs but are carriers who can pass the mutation to their offspring. When two carriers are bred, each puppy has a 25% chance of being affected by PRA-crd2, a 50% chance of being a carrier, and a 25% chance of being free of the mutation. For ethical breeding practices, it is recommended to avoid mating carriers to prevent the perpetuation of this condition in the breed. Testing and informed breeding choices are essential to reduce the incidence of PRA-crd2 in future generations, ensuring puppies are not at risk for developing this incapacitating eye disorder.
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.