Canine multifocal retinopathy 3 / CMR3 (BEST1-related) - Dog

What does this test examine?

This genetic test analyses two BEST1 variants, c.1466G>T and c.1388delC, used together for CMR3 in dogs. The disorder is also known as canine multifocal retinopathy, multifocal retinopathy, CMR and BEST1-related retinopathy. CMR3 is especially relevant in Finnish Lapphund, Lapponian Herder and Swedish Lapphund.

What does CMR mean for the dog?

CMR is an inherited eye disorder in which multiple small areas develop in or beneath the retina. Eye examination can show round grey-tan, orange, tan-pink or pink lesions that resemble blisters or local retinal detachments. These changes are often seen at a young age. Many dogs function well, but the finding is important for breeding selection, eye screening and recognising inherited risk within a line.

Inheritance and result

CMR is inherited as an autosomal recessive trait. A dog with one copy is a carrier and can pass the variant on without being affected. A dog with two copies of the relevant variant develops the corresponding CMR form. Other eye findings can look similar, so a genetic result adds practical value beside the visible ophthalmic findings.

Practical value of this test

• Helps breeders identify carriers early and avoid risk matings.
• Supports selection of combinations in which affected puppies are not expected.
• Gives owners and veterinarians clear context when retinal spots, blisters or retinal folds are seen during eye examination.
• Makes communication about CMR1, CMR2 or CMR3 unambiguous because each form is defined by a different BEST1 variant.
• Is useful for lines in which related dogs, parents or offspring have a CMR result or eye finding.