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Masticatory Mysositis

Dear Dr. Mike:
I have a 5 year old S. Munsterlander who was diagnosed with Masticatory Mysositis about a year ago. He never showed any signs of discomfort but I noticed the change in the muscle structure of his head and took him in to check it out. They put him on Pregnizone (sp?) for about 7 weeks. There seems to be little or no change except for muscle spasms. I noticed a couple times last year that when he was lying down, he would tremble a little, like he was cold. Our female, living under the same conditions showed no sign of being cold. The frequency of these episodes is increasing to the point that he will shake at least a little every time he lays down to go to sleep. After 5-15 minutes the spasms stop. He seems to be resting fine except every few minutes his upper leg muscles will tighten and tremble for a few moments. These will occur even when he has been in the house for several hours before hand so I don't think it is temperature related. If he is up and moving around, I don't see any sign of the shakes.
Any ideas???
Thanks for your help.

Tom, As you have probably learned, we don't know what causes masticatory myositis (also called eosinophilic myositis). We suspect an autoimmune problem (allergic to yourself like lupus in people) is causing the inflammation of the chewing muscles that is characteristic of the disease. For most affected dogs it is very painful to open their mouths, they may also show wasting of the muscles associated with chewing. A definite diagnosis is made by doing a muscle biopsy. The prognosis is usually good if dogs are treated early in the disease with high doses of corticosteroids. The dosage should be tapered slowly, watching for signs of reoccurrence. It doesn't sound like what your dog is doing now is related to the masticatory problem, I think unless you see that it bothers the dog than "benign neglect" the prescription. Thanks for the question.

Dr. Mike

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