Centronuclear Myopathy (CNM)
Centronuclear Myopathy (CNM) is an inherited progressive muscle disease affecting Labrador retrievers. Though the severity of symptoms is variable, affected dogs typically present between 6 weeks to 7 months of age with exercise intolerance, awkward gait and difficulty eating. As the disease progresses, symptoms also include generalized muscle Atrophy, downward flexion of the head and neck, low muscle tone and more frequent episodes of collapse when exposed to cold temperatures. Progression of the disease tends to stabilize around one year of age and dogs typically have a normal life span, but affected dogs usually have life-long medical problems due to the underlying muscle disease.
Breed-Specific Information for the Labrador Retriever
The Mutation of the PTPLA gene associated with centronuclear Myopathy has been identified in Labrador retrievers. Though the frequency in the overall Labrador retriever population is unknown, in one study from 2010-2012 of 1,757 Labradors tested from the United States, United Kingdom, Canada, Ireland and continental Europe, 13.9% were carriers of the mutation.
Genetic testing of the PTPLA gene in Labrador retrievers will reliably determine whether a dog is a genetic Carrier of centronuclear Myopathy. Centronuclear Myopathy 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 PTPLA gene mutation. Reliable genetic testing is important for determining breeding practices. 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. Labrador retrievers 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.
- Gentilini F, Zambon E, Gandini G, Rosati M, Spadari A, Romagnoli N, Turba ME, Gernone F.Frequency of the allelic variant of the PTPLA gene responsible for centronuclear myopathy in Labrador Retriever dogs as assessed in Italy. J Vet Diagn Invest. 2011 Jan; 23(1):124-6. [PubMed: 21217042]
- Maurer M, Mary J, Guillaud L, Fender M, Pele M, Bilzer T, Olby N, Penderis J, Shelton GD, Panthier JJ, Thibaud JL, Barthelemy I, Aubin-Houzelstein G, Blot S, Hitte C, Tiret L. Centronuclear myopathy in Labrador retrievers: A recent founder mutation in the PTPLA gene has rapidly disseminated worldwide. PLoS One. 2012;7(10):e46408. doi:10.1371/journal.pone.0046408. [PubMed: 23071563]
- Pelé M, Tiret L, Kessler JL, Blot S, Panthier JJ. SINE exonic insertion in the PTPLA gene leads to multiple splicing defects and segregates with the autosomal recessive centronuclear myopathy in dogs. Hum Mol Genet. 2005 Jun 1; 14(11):1417-27. [PubMed: 15829503]