Centronuclear myopathy in Labrador Retrievers is a recessively inherited muscular disease.
This disease was previously known as Labrador muscular myopathy. The disease is characterized by early-onset muscular problems such as awkward gait, fatigue, and difficulty eating. Affected puppies generally begin displaying these problems within a few months after birth.
Researchers in France, Drs. Tiret and Blot at The Alfort School of Veterinary Medicine discovered the mutation that is responsible for the disease. The test offered here is based on this discovery.
As with other recessive diseases, animals with two copies of the mutation will be affected and display symptoms, whereas animals with one copy (carriers) and no copies (clear) will be symptom-free.
The dog has 2 copies of the normal gene and will neither develop CNM nor pass a copy of the CNM gene to any of its offspring.
The dog has one copy of the normal gene and one copy of the mutant gene that causes CNM. It will not develop CNM but will pass on the CNM gene to 50% (on average) of its offspring.
Carriers can still be bred to clear dogs. On average, 50% of such a litter will be clear and 50% carriers; there can be no affected puppies produced from such a mating. Dogs which will be used for breeding can themselves be DNA tested to determine whether they are clear or carrier.
The dog has two copies of the CNM mutation and is affected with CNM. It will develop CNM at some stage during its lifetime, assuming it lives to an appropriate age.