Multifocal Retinopathy 2

Other Names: Canine multifocal retinopathy 2, CMR2
Affected Genes: BEST1
Inheritance: Autosomal Recessive
Mutation: Point Mutation
Breed(s): Coton de Tulear

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Common Symptoms

Multifocal retinopathy 2 is an inherited disorder of the Retina affecting dogs. Affected dogs typically present around 15 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 or 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 2.


Testing Tips

Genetic testing of the BEST1 gene will reliably determine whether a dog is a genetic Carrier of multifocal retinopathy 2. Multifocal retinopathy 2 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. Dogs 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

  • Guziewicz KE, Zangerl B, Lindauer SJ, Mullins RF, Sandmeyer LS, Grahn BH, Stone EM, Acland GM, Aguirre GD. Bestrophin gene mutations cause canine multifocal retinopathy: a novel animal model for best disease. Invest Ophthalmol Vis Sci. 2007 May; 48(5):1959-67. [PubMed: 17460247]
  • Zangerl B, Wickström K, Slavik J, Lindauer SJ, Ahonen S, Schelling C, Lohi H, Guziewicz KE, Aguirre GD. Assessment of canine BEST1 variations identifies new mutations and establishes an independent bestrophinopathy model (cmr3). Mol Vis. 2010 Dec 16; 16:2791-804. [PubMed: 21197113]