Is Masticatory Myositis Fatal

Masticatory myositis can be fatal as the dog cannot open its mouth to eat or drink properly. If the disease goes untreated or it has progressed to the point that most of the muscle fibers of the jaw have been replaced by fibrous tissue, this disease is not curable.

The condition occurs in males and females, with an average age of onset of 3 years, though puppies as young as 4 months have been affected. Fortunately, if MMM is diagnosed early, dogs can be treated to increase the likelihood of a full recovery. Research of this disease at the University of California-San Diego led to the development of a blood test in 2004 that detects the presence of 2M antibodies and accurately identifies affected dogs.

An accurate diagnosis is important in treating dogs with MMM. Early detection and aggressive immunosuppressive therapy can help reduce myofiber loss and muscle fibrosis, which can lead to irreversible jaw dysfunction and severe muscle atrophy.

As with Page’s Golden Retriever Buddy, an accurate diagnosis and prompt treatment are vital to help a dog regain the ability to open his mouth without pain. Corticosteroids, particularly prednisone, are the cornerstone of therapy, Shelton says. During the acute phase, corticosteroids help to achieve aggressive immunosuppression.

Masticatory muscle myositis is an autoimmune disorder in which antibodies attack the 2M fibers in the masticatory (chewing) muscle group. A blood test was developed in 2004 by researchers at the University of California-San Diego to confirm the circulating antibodies that attack 2M fibers. The test is available to veterinarians through the Comparative Neuromuscular Laboratory at the University of California at San Diego. For information, visit http://medicine.

1 Melmed C, Shelton GD, Bergman R, Barton C. Masticatory Muscle Myositis: Pathogenesis, Diagnosis and Treatment. Compendium. 2004:590-605.

What is Masticatory Muscle Myositis in Dogs?

Masticatory Muscle Myositis is an autoimmune disease or process where the immune system targets the masticatory muscle (a large muscle in the jaw). Dogs suffering from this disease will often present in the clinic with jaw pain, lack of eating, or a complete inability to even open their jaw!

Source: Vetfolio

However, what is up and down with this sometimes overlooked disease? Take a read below and learn more about the issues with this canine masticatory muscle myositis!

How is MMM diagnosed?

A dog’s inability to open his mouth, inability to eat, swollen chewing muscles, and excruciating face pain are symptoms of MMM. A blood test will diagnose MMM. The test searches for and measures circulating antibodies that attack the muscle fibers (autoantibodies). The blood test must be done before any treatment is provided, as treating with corticosteroid anti-inflammatory medication may cause the blood test to register a false negative.

In cases where circulating autoantibodies are not detected, there is another diagnostic test for MMM, a muscle biopsy. The veterinarian removes a small section of affected muscle for evaluation. The muscle biopsy is used to determine the level of inflammation present as well as the severity of the fibrosis that occurs as the muscle tissue deteriorates.


Can a dog live with MMM?

“MMM generally responds initially to therapy, but relapses occur quickly if treatment is discontinued prematurely.” “If the disease is diagnosed early and a dog is treated appropriately, the prognosis is good for dogs with MMM,” Greenfield says. “In these cases, dogs can usually regain normal jaw mobility and function.

How quickly does MMM progress in dogs?

In the study, MMM generally carried a favorable prognosis when treated promptly with immunosuppressive doses of prednisone. Dogs typically regained normal masticatory function within 4 weeks of treatment, although 27% of affected dogs experienced relapse that resolved with continued glucocorticoid therapy.

Can MMM in dogs go away on its own?

If MMM is diagnosed early and treatment is initiated right away, a dog usually regains normal jaw function and the ability to open and close his mouth without pain. In some dogs, scar tissue can form within the masticatory muscles causing permanent problems.