Multifocal Retinopathy 1

Other Names: Canine multifocal retinopathy 1, CMR1
Affected Genes: BEST1
Inheritance: Autosomal Recessive
Mutation: chr18:54478586 (canFam3): C>T

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Common Symptoms

Multifocal Retinopathy 1 is an inherited disorder of the Retina affecting multiple breeds of dog. Affected dogs typically present between 11 and 16 weeks of age with multiple discrete circular areas of retinal detachment with underlying fluid accumulation that are visible on an eye exam performed by a veterinarian. These blister-like lesions are typically found in both eyes and can appear gray, tan, orange nor pink and vary in number, size and location. Progression of retinal changes is usually slow and new lesions are not noted after 6 to 12 months of age. Occasionally as affected dogs age, lesions appear to heal and are no longer visible on an eye exam. Generally the dog’s vision is not affected although vision loss has been described in some cases of multifocal retinopathy 1.

Breed-Specific Information for the Miniature American Shepherd

Miniature American Shepherd is included as a breed susceptible to multifocal retinopathy 1 because of its close relatedness to the Australian Shepherd breed, which is known to develop this disease due to Mutation of the BEST1 gene. The frequency of the causal mutation in the general Miniature American Shepherd population is unknown.

Testing Tips

Genetic testing of the BEST1 gene in Miniature American Shepherds will reliably determine whether a dog is a genetic Carrier of multifocal retinopathy 1. Multifocal Retinopathy 1 is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the BEST1 gene mutation. Reliable genetic testing is important for determining breeding practices. Because visual deficits are generally not noted and lesions can regress as affected dogs age, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Miniature American Shepherds that are not carriers of the mutation have no increased risk of having affected pups.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.

References

  • Donner J, Kaukonen M, Anderson H, Moller F, Kyostila K, Sankari S, Hytonen M, Giger U, Lohi H. Genetic Panel Screening of Nearly 100 Mutations Reveals New Insights into the Breed Distribution of Risk Variants for Canine Hereditary Disorders. PLoS One. 2016 Aug 15;11(8):e0161005. [PubMed: 27525650]
  • Gornik KR, Pirie CG, Duker JS, Boudrieau RJ. Canine multifocal retinopathy caused by a BEST1 mutation in a Boerboel. Vet Ophthalmol. 2013 Sep 3. doi: 10.1111/vop.12095. [PubMed: 23998685]
  • Grahn BH, Philibert H, Cullen CL, Houston DM, Semple HA, Schmutz SM. Multifocal retinopathy of great Pyrenees dogs. Vet Ophthalmol. 1998;1(4):211-221. [PubMed: 11397233]
  • Guziewicz KE, Slavik J, Lindauer SJ, Aguirre GD, Zangerl B. Molecular consequences of BEST1 gene mutations in canine multifocal retinopathy predict functional implications for human bestrophinopathies. Invest Ophthalmol Vis Sci. 2011 Jun; 52(7):4497-505. [PubMed: 21498618]
  • Hoffmann I, Guziewicz KE, Zangerl B, Aguirre GD, Mardin CY. Canine multifocal retinopathy in the Australian Shepherd: a case report. Vet Ophthalmol. 2012 September; 15(0 2): 134–138. [PubMed: 22432598]