Dear Dr. Thompson,
I have a question about masticatory muscle myositis (MMM). My 2-year-old Golden Retriever was just diagnosed with this disease. He was a very healthy young male who was not dealing with any issues and this came on out of the blue. Upon thinking back to when the symptoms first developed, he had just received some vaccinations. I have been hearing from people who are indicating that many of these autoimmune disorders appear after a dog has had recent vaccinations. I don’t believe that it was just a coincidence and wonder if it was the combination of the vaccines. He has had vaccinations in the past without a problem. I am now not sure about him receiving any future vaccinations because of this autoimmune disorder. Do you have any thoughts on this?
Masticatory muscle myositis (MMM) is a disease where the body develops antibodies to a very specific muscle fiber called the 2M fiber and the subsequent inflammation leads to progressive damage and scarring. These fibers are only in the muscles involved with eating called the temporal, masseter, and ptyergoid.
Symptoms are pain on opening the mouth, trouble eating, and limited motion of the jaw. Diagnosis is made with a very specific blood test for the 2M muscle antibodies. Treatment focuses on using immunosuppressive medications like prednisone and azathioprine. Once normal jaw function returns, it is generally needed for up to four to six months and the occasional relapse may occur.
Your question as to whether or not this may be related to his recent vaccinations is somewhat less straightforward than his diagnosis in this case. This is an immune-mediated disease and has what is called a humoral response. This response is also what is triggered with immunization against diseases, but it is important to state that this does not imply a direct cause-and-effect relationship.
Because the immunologic response in this disease is focused on a very specific muscle fiber and certain breeds are more commonly affected, recent research into MMM and a similar condition affecting the general muscles of the body has suggested that certain genes are involved and are triggered into expression. This means that this is likely an inherited condition that is waiting for an opportunity to develop and what would be a normal immune reaction to vaccination might have been that trigger.
For the overwhelming majority of animals that do not have these genes, immunizations are safe and critical in preventing a number of devastating infectious diseases, many of which can be fatal or contagious to people.
Going forward, you and your veterinarian need to determine his risk factors for certain diseases coupled with the potential for triggering a relapse of his MMM. It sounds as if you have come to a diagnosis relatively quickly and for the vast majority of cases management is very rewarding. I hope your boy does well.
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