Canine Multifocal Retinopathy (CMR)
Canine Multifocal Retinopathy (CMR) is an autosomal recessive eye disorder known to affect Great Pyrenees, English Mastiffs, Bullmastiffs, Australian Shepherds, Dogue de Bordeaux, English Bulldogs, American Bulldogs, Coton de Tulears, Perro de Presa Canario, and Cane Corsos.
The mutation causes raised lesions to form on the retina which alters the appearance of the eye but usually does not affect sight. The lesions may disappear, or may result in minor retinal folding. Symptoms of the mutation usually appear when a puppy is only a few months old, and generally do not worsen over time.
CMR is recessive, so both parents would need to be carriers of the mutation to produce an affected puppy. "Clear" CMR dogs do not carry the mutation for the disorder. Breeding two clears or one clear and one carrier will not produce affected offspring, however if one parent is a carrier, a percentage of the offspring will be carriers. Therefore, it is useful to test for the presence of the CMR mutation before breeding. Additionally, since retinal defects can be caused by other conditions, testing can verify that a dog actually has CMR rather than some other eye condition.
Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at Canine Test Now.
Test Is Relevant to the Following Breeds:
There are two types of CMR: CMR Type 1 and CMR Type 2. Which type you should test for depends on the breed:
Type 1: Great Pyrenees, English Mastiffs, Bullmastiffs, Australian Shepherds, Dogue de Bordeaux, English Bulldogs, American Bulldogs, Perro de Presa Canario, and Cane Corsos
Type 2: Coton de Tulears
Animal Genetics offers DNA testing for Canine Multifocal Retinopathy Types 1 and 2. The genetic test verifies the presence of the recessive mutation and presents results as one of the following:
|CMR/CMR||Affected||The dog carries two copies of the mutant gene and is homozygous for CMR. This dog will be affected and will always pass on a copy of the mutated gene to its offspring.|
|CMR/n||Carrier||Both the normal and mutant copies of the gene detected. Dog is a carrier for the CMR mutation and can pass on a copy of the defective gene to its offspring 50% of the time.|
|n/n||Clear||Dog tested negative for the gene mutation that causes CMR and will not pass on the defective gene to its offspring.|