Newly diagnosed with masticatory myositis

[Davisk]

My sweet 2 year old yellow lab has been newly diagnosed with masticatory myositis. We brought rowdy to the vet after noticing him having trouble opening his mouth. We've had this issue with him about six months ago, we took him to the vet they gave him an antibiotic and an anti-inflammatory and we were on our way. Rowdys jaw issues cleared up in about 3-5 days and he was back to his usual self. Recently we noticed his head lookin very "bumpy" it looked as if he was getting knots on the top and sides of his skull. (Actually was atrophy of his muscles surrounding his skull and jaw) Along with that his jaw started acting up, so back to the vet we went. Our vet diagnosed him with masticatory myositis. The treatment for this autoimmune disease is prednisone. Chronic prednisone therapy. I've being doing my research and have read that a common side effect of prolonged steroid use is cushings disease. Does anyone here have any experience with this? Advice?

[labblab]

Hello and welcome to you and Rowdy, although I am very sorry for the problems that have brought you to us. I had not previously known about masticatory myositis, but I have just finished doing some very quick reading -- which I am sure you have also been doing yourself. :o

Yes, it is indeed true that longterm use of prednisone can produce symptoms identical to naturally occurring Cushing's, and we have seen dogs here who have been afflicted in this way. Typically, the Cushing's symptoms resolve once the steroid is discontinued. But of course the treatment path is trickier if there is no good alternative to prednisone.

However, even with my short reading about this disorder, one thing I've seen is that appropriate management of the dosing/timing of the prednisone therapy is key, and that dogs may not need to continue on the pred forever just so long as the drug is managed properly in the first place. So you will want to make sure that somebody really knowledgeable is directing the therapy, whether it be your vet or a referral specialist.

For instance, of course I do not know all the facts, but my first question from my own reading would be, is there a reason why your vet chose against treating with prednisone the first time around? Had the disorder been treated with pred initially, perhaps the relapse and additional muscle atrophy would not have occurred. It does seem really important to tailor the pred therapy appropriately, and relatively large doses may be required initially in order to gain control and halt disease progression.


Inappropriate dosages of corticosteroids for inappropriate periods of time are commonly encountered problems and result in relapse of the disorder and worsening of the fibrosis. The best way to achieve a favorable outcome with MMM is an early diagnosis and correct treatment.

You may have already seen these articles, but here are a couple of links that seemed helpful to me.

http://www.vetsonline.com/publications/veterinary-times/archives/n-43-35/masticatory-muscle-myositis-in-dogs.html

http://vetneuromuscular.ucsd.edu/cases/1999/may99.html

Please keep us updated as treatment proceeds for Rowdy, and hopefully any ill effects from the prednisone can be kept to a minimum and the drug totally discontinued after a period of time.

Marianne