Canine Multifocal Retinopathy 2

Canine multifocal retinopathy 2 is an ocular disease caused by the c.482G>A mutation in the bestrophin 1 gene that causes degeneration in multiple areas of the retina.

Symptoms

Affected dogs usually present with multiple bilateral circular multifocal areas of retinal detachment between 11 and 16 weeks of age. Tan-brown and orange deposits are seen underneath the retina. Degeneration is slow and usually does not lead to blindness. Most dogs do not show visual problems; exceptionally, in more severe cases, there may be visual disturbances.

Disease Management

In case your dog shows any symptoms, you should visit your veterinarian for evaluation.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Canine multifocal retinopathy (cmr) type 2 is an ocular disorder characterized by multiple areas of retinal degeneration. It belongs to a group of retinal diseases called bestrophinopathies, which can also occur in humans. This disease is caused by three different mutations in the BEST1 gene, which codes for a protein known as bestrophin 1, typical of the retina and which have led to the naming of three distinct forms of the disorder (cmr1, cmr2 and cmr3). All three forms are very similar clinically, but the last two only occur in one race. cmr2 is caused by the c.482G>A mutation which changes an evolutionarily conserved glycine residue to aspartic acid. This mutation may be present in Coton de Tuléar dogs.

Most affected breeds

Coton de Tulear

Bibliography

Guziewicz KE, Slavik J, Lindauer SJ,et al. Molecular consequences of BEST1 gene mutations in canine multifocal retinopathy predict functional implications for human bestrophinopathies. Invest Ophthalmol Vis Sci. 2011 Jun 23;52(7):4497-505.

Majchrakova Z, Hrckova Turnova E,et al. The incidence of genetic disease alleles in Australian Shepherd dog breed in European countries. PLoS One. 2023 Feb 27;18(2):e0281215.

Miyadera K, Acland GM, Aguirre GD. Genetic and phenotypic variations of inherited retinal diseases in dogs: the power of within- and across-breed studies. Mamm Genome. 2012 Feb;23(1-2):40-61.