Craniomandibular osteopathy is an inherited skeletal syndrome affecting dogs. Affected dogs often present at around four to eight months of age with signs of discomfort when eating or chewing caused by abnormal bone proliferation of the mandible, occipital and temporal skull bones, and/or the tympanic bulla (the bony structure housing the middle and inner ear). Other clinical signs of craniomandibular osteopathy include swelling around the jaw, difficulty opening mouth, drooling, fever, and difficulty holding food or toys with the mouth. Most dogs experience a cessation of bony growth around one year of age and the growth may recede or resolve in some cases with or without treatment. Although most cases of craniomandibular osteopathy are non-fatal, jaw pain in affected dogs may result in a reluctance to eat and secondary malnutrition. In some cases, pain and malnutrition may influence caregivers to pursue euthanasia due to quality of life concerns.
Genetic testing of the SLC37A2 gene will reliably determine whether a dog is a genetic Carrier of craniomandibular osteopathy. Craniomandibular osteopathy is inherited in an autosomal incomplete dominant manner in dogs meaning that dogs only need to inherit one copy of the mutated gene to be at an increased risk of developing the disease. Though the disease is most commonly seen in dogs having two copies of the mutated gene, carrier dogs can also experience abnormal bony proliferation. Thus, dogs that have one or two mutant copies of the gene are considered at-risk for craniomandibular osteopathy. When carriers of this Mutation are bred with another dog that also is a carrier of the same mutation, there is risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance that the puppy will inherit two copies of the mutation and a 50% chance that the puppy will inherit one copy of the mutation and, in either case, may be susceptible to craniomandibular osteopathy. 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 is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups when bred to a dog that is also clear for this mutation.
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.
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