Cone Rod Dystrophy 1 and 2

Quick Summary

Cone Rod Dystrophy 1 and 2 cause early onset retinal degeneration leading to blindness in the American Staffordshire Terrier and American Pit Bull Terrier.

Phenotype: Cone Rod Dystrophy 1 and 2 cause early onset retinal degeneration leading to blindness in the American Staffordshire Terrier and American Pit Bull Terrier. Visual impairment can be observed at less than one year of age with severe blindness by early adulthood.

Mode of Inheritance: Autosomal recessive

Alleles: N = Normal, CRD1 = Cone Rod Dystrophy 1 (American Staffordshire Terrier); CRD2 = Cone Rod Dystrophy 2 (American Pit Bull Terrier)

Breeds appropriate for testing: American Pit Bull Terrier, American Staffordshire Terrier, and dogs derived from those breeds

Explanation of Results:

  • Dogs with N/N genotype will not have cone rod dystrophy 1 or cone rod dystrophy 2 and cannot transmit those variants to their offspring.
  • Dogs with N/CRD1 genotype will not be affected by cone rod dystrophy 1, but are carriers. They will transmit this CRD1 variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% cone rod dystrophy 1-affected puppies.
  • Dogs with CRD1/CRD1 genotype will have cone rod dystrophy 1, a condition leading to blindness.
  • Dogs with N/CRD2 genotype will not be affected by cone rod dystrophy 2, but are carriers. They will transmit this CRD2 variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% cone rod dystrophy 2-affected puppies.
  • Dogs with CRD2/CRD2 genotype will have cone rod dystrophy 2, a condition leading to blindness.

Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)

Price

$50 one test per animal
$30 as additional test (same animal)
$45 for 3 or more dogs

Additional Details

Early onset retinal degeneration in the American Staffordshire Terrier (cone rod dystrophy 1, crd1) and American Pit Bull Terrier (cone rod dystrophy 2, crd2) result from mutations in PDE6B and IQCB1 respectively. Visual impairment can be observed at less than one year of age with severe blindness by early adulthood. Both mutations have an autosomal recessive mode of inheritance and thus males and females are equally affected. Carriers (with one copy of defective gene) have no apparent visual impairment and can only be detected through genetic testing. Within each breed, crossing of carriers is predicted to produce 25% affected offspring. Because the mutations are in different genes and thus independent from each other, a dog with one copy of each mutation will not be affected and crossing carriers of crd1 with carriers of crd2 will not produce affected offspring.

Turnaround Time
3-6 business days

Species

Dog

Type of Test

Results Reported As

 

Test Result Cone Rod Dystrophy 1
N/N Normal. No copies of the crd1 mutation.
N/CRD1 Carrier. 1 copy of the crd1 mutation. Dog is normal.
CRD1/CRD1 Affected. 2 copies of the crd1 mutation. Dog will go blind.
Test Result Cone Rod Dystrophy 2
N/N Normal. No copies of the crd2 mutation.
N/CRD2 Carrier. 1 copy of the crd2 mutation. Dog is normal.
CRD2/CRD2 Affected. 2 copies of the crd2 mutation. Dog will go blind.
References

Goldstein, O., Mezey, J.G., Schweitzer, P.A., Boyko, A.R., Gao, C., Bustamante, C.D., Jordan, J.A., Aguirre, G.D., & Acland, G.M. (2013). IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Investigative Ophthalmology & Visual Science, 54(10), 7005-7019. doi: 10.1167/iovs.13-12915