How to Recognize Canine Masticatory Myositis


Canine masticatory myositis is a condition in which your dog cannot open his mouth. Because there are a number of problems which may cause similar symptoms, a dog which is suspected of having this extremely serious condition needs to be evaluated by a veterinarian. Something as simple as a stick caught in his mouth can masquerade as this disease. It is important to be sure.

Despite the fact that canine masticatory myositis is an immune system disease, the effects of it are only seen in the masticatory, or chewing, muscles. These muscles are unique in the body because they contain muscle fibers called “2M.” These particular fibers do not exist anywhere else in the dog’s body, so when they are attacked by the immune system the symptoms affect only the dog’s head and jaws.

How to Pick Out Canine Masticatory Myositis

Canine Masticatory Myositis

The onset of symptoms typically occurs when the dog is about 3 years old. Several breeds seem particularly vulnerable to this condition: German shepherd, golden retriever, bearded collie, Doberman pinscher, Cavalier King Charles spaniel, Old English sheepdog, and Labrador retriever, though other breeds may also suffer from it. Use the age of the dog only as a guide, as onset may occur in a dog which is older or younger than the typical age for this disease.

During the acute stage of this disease the dog’s masticatory muscles will be swollen and the dog’s eyes will appear to bulge due to the pressure from the swollen muscles behind them. You dog may also have some lymph node swelling and a fever at this point, but he may or may not be in any pain. The disease is often not identified during the acute stage because the change in the dog’s appearance may happen gradually enough that it is not immediately noticed. Also, people often expect that in an immune system disease both sides of the head would be involved, but this is not necessarily true. When symptoms appear on only one side of the head it can be deceptive.

As masticatory myositis progresses symptoms become more pronounced. The dog becomes unable to eat. His jaw will be effectively locked shut due to the disease and may not be able to be pried open, nor even opened under general anesthetic. The masticatory muscles become atrophied, or shriveled, due to lack of use. The dog’s head will begin to look thin and skeletal. Even if the disease is only on one side, since the dog cannot use the muscles on either side of his face his whole head will take on the same appearance. If you have any doubts about your pet’s health, take it to a veterinarian as soon as possible.