Stewart Has Polymyositis

[midoamy]

Hello all. I am very involved in dog rescue in Ohio...primarily helping to get dogs who are slated for euthanasia out of the shelter in Columbus. In August of 2017 I watched a video of a big brown dog listed as a Pit Bull mix. He was on the list for medical...due to severe masticatory wasting, the shelter vet suspected Masticatory Myositis. He was going to be put down and given his sweet nature I called rescues to get him out for me til I found one that would. After several vet visits he was diagnosed with Polymyositis. He was diagnosed via muscle biopsy. He also had a cancerous mast cell tumor taken from his rear leg. We suspect that it brought on the Myositis. Tests of the lymph node right under the tumor showed that it had not spread. The wound took a very long time to heal and now I am at a point where I could start Prednisone. However, Stewart is up to 70 pounds. I make all his food myself as he has trouble with dry and doesn't seem super interested in canned food. He plays like a puppy....he has improved so much that I find myself wondering if we should do Pred.

My main problem is that I have no baseline other than the positive changes since August. The only active sign of the disease is some involuntary muscle movement in his rear legs when he is standing. The shelter vet thought he was about 5 years old and breedwise, I suspect that he is half Cane Corso...his appearance is much more along those lines than a Pit. I'm just not certain how I will identify an improvement when he is currently doing so well. Also, despite all the muscle wasting in his head, he had full range of motion in his jaws under anesthesia. The vet estimates a total muscle loss of 15-20 pounds.

This dog has clearly been abused and was going to be put down 6 months ago...I hate to put him on Pred when he is quite literally having the time of his life. I'm just not sure what to do and the vet has never treated the disease before.

[Jo CIMDA]

Hi and welcome to you and Stewart.

Wow poor Stewart, and good on you for all you have done for him. 

Stewart isn't showing typical signs of masticatory muscle myositis (MMM) or polymyositis. It seems strange that his head muscles are affected and yet his jaw muscles aren't.

Myositis is a very painful AI disease and it gets progressively worse and more debilitating, and more painful as time goes on.    This doesn't sound like Stewart's symptoms and yet if it has been confirmed by a biopsy then why isn't he deteriorating?   What do you think?

If polymyositis  is not treated it invariably affects the muscles in the throat causing megaoesophagus and the dog has great difficulty in swallowing.  This is a symptom that is not usually reversible even after resolution of the disease. 

The following is very interesting:

http://www.vetbook.org/wiki/dog/index.php/Polymyositis

In dogs, a number of reports have linked polymyositis with lymphoma[9][10], thymoma[11], myeloid leukemia, bronchogenic carcinoma, tonsillary carcinoma[12], anaplastic round cell tumor and plasmacytoma[13]. These diseases may well result in secondary infiltration of muscle fibres with inflammatory byproducts.

I agree with you.  Personally, I would be loathed to treat with immunosuppressive dose of prednisolone if Stewart is as well as you describe.   However, I will copy the best immunosuppressive drug protocol I have come across by Michael J Day, Professor of Immunology, Bristol Vet School.   The drug used in this protocol is prednisolone, but some consideration should be given to a side effect of prednisolone which is muscle weakness and therefore AI diseases that affect the muscles such as myositis and myasthenia Gravis (a neuromuscular disease)  are often treated with a combination of immunosuppressive drugs such as Leflunomide, or mycophenolate, Cyclosporin etc... and a lower dose of prednisolone.   

Jo


Example: Reduction Protocol for prednisolone:
Clinical Immunology of the Dog & Cat , 2nd Edition,  by Michael J Day
Professor Michael DayBSc, BVMS(Hons), PhD, DSc, DiplECVP, FASM, FRCPath, FRCVS 

Professor of Veterinary Pathology, University of Bristol, UK and WSAVA - Chairman of Scientific Advisory Committee.
This example is based on a dog receiving an induction dose of 1.0mg/kg/q 12hrs (q = every)
Dose                           Duration (based on clinical effect)
1.0mg/kg/q 12h                          10-28 days
0.75mg/kg/q 12h                       10-28 days
0.5mg/kg/q 12h                         10-28 days
0.25mg/kg/q 12h                        10-28 days
0.25mg/kg/q 24h                        10-28 days
0.25-0.5mg/kg EOD                    at least 21 days
0.25-0.5 mg/kg every third day      at least 21 days

Every reduction is made after consideration to improvement of clinical signs, blood results and side effects of the drugs.

"Doses above 2.2mg/kg/day do not give more immunosuppression but do cause more side effects. Many internists believe that prednisolone doses should not exceed 80mg per day, regardless of the dog's weight."  Plumb's Veterinary Drug Handbook Eight Edition.

[midoamy]

Thank you so much for your response. Information is so difficult to find on myositis...I love to research and I had actually read the article you linked to. I've been through just about everything there is to read on it. So much of the information out there doesn't go much further than defining it. I'm much more interested in actual cases, treatments and their outcomes and there is almost no information along those lines so I was very grateful to find this group.

Again,  with this dog I am only working with a baseline of around 6 months. He was picked up as a stray so there is no owner surrender info either. He was drooling uncontrollably when he first got here...that has stopped. I noticed that when he would pant, his tongue was always uneven. He was also aspirating his own saliva, water and food. He seemed to have a very hard time with a normal food dish with straight sides. I started feeding him in a large pasta bowl with gently sloping sides and then went to a (very large) raised feeder and that has helped tremendously. He would be very easily winded after a short run in the yard as well.

He still isn't too keen on picking anything up to carry, but a few months ago he showed some interest in chewing and will chew on bully sticks. I didn't want him to be in pain so I asked for a gabapentin prescription and he gets 300 Mg in the morning. He also get 3 Benadryl Tablets twice a day, as his cancer was allergenic in nature.

For food, I throw a bunch of frozen meat in the crockpot once a week or so. Cook it till it is falling off the bones, then I go through with metal tongs and pick out any bones. Sometimes with poultry I am able to pulverize the bones and add them to the food. It makes a very nice bone broth/stock that is often a thick jelly. I pack the meat in one container and top off with stock to keep it soft. The stock goes in a bigger container. At mealtime (I am feeding three dogs) I start with a bit of rice, a sprinkle of quick cooking oats and water. Once soft, I add stock, meat and a fresh fruit or veggie. I have used grated apple, peas, carrots, green beans, blueberries, spinach and many others. I watched a Ted Talk with the fellow who has had the last several Guinness world record holding dogs...he feeds kibble with a fresh fruit or veggie every day...figured it can't hurt. I also use a few spoonfuls of Honest Kitchen freeze dried dog food for a thickener and nutrition as well as some high quality dry dog food (I like Fromm Family). I add a smidge of seameal powder supplement too. I let it all cool down/soften then feed. If I haven't prepped meat, I use the high fat ground beef and add it to my mix raw. I make homemade liver treats and frozen ones from peanut butter, greek yogurt and banana. I make those in mold that fits into a kong perfectly.  They also get a fish oil capsule once daily.

I'm not sure why he isn't deteriorating the way he should be. I know his symptoms don't really fit inside the box. I have read that Myositis can be both a cause and a symptom of cancer...I'm not at all sure what to think. I'm not sure if his reluctance to carry toys is pain related or if he's simply lost so much muscle that he can't do it. I will say that I have never heard him whimper while chewing etc...

The myositis was confirmed with two biopsies done while he was getting his tumor removed, as well as being neutered. Poor guy. He wasn't a happy camper at all.

At this point, I am leaning towards no Prednisone....I am a quality of life person and as long as he is doing well, I don't feel a need to put him through that.

[Jo CIMDA]

Hi

Stewart lives like a king for sure.  It sounds a wonderful diet.

I had a dog with MMM and it started with his inability to open his mouth wide.  We didn't suspect MMM until a lot later (this was back in the 1990's).  My vet treated him speculatively but then his whole body swelled and he went to the Royal Veterinary College where they finally diagnosed him with SLE, a multisystemic AI disease.  He had so much wrong with him. He lived for four more years after correct treatment.

I don't understand what has halted the progression of Stewart's myositis.  I would be loathed to start immunosuppressive therapy until he needs it.

Good luck
Jo

[midoamy]

Stewart doesn't open his mouth fully when he yawns...I would say maybe 2/3 of what is normal and there is a sound with it. Not a pleasant sound. I also still observe some involuntary muscle movement in his hindquarters when he is standing up, but not lying down. I want to think that whatever he has going on has stopped, but given the involuntary muscle movement, I have to wonder if he has something else going on. My understanding is that untreated, Polymyositis should have killed him by now and that he should be worse not better. I also know that the prognosis for any kind of Myositis mixed with cancer is very guarded. I want to do something about it so badly, but am unwilling to upset his current quality of life just so I can feel proactive. Should he turn out to need immunosuppressive therapy, I will be very glad to have the guidelines you gave me.

I do have one more question. I have been thinking of Myositis as a disease...but browsing this forum I get the impression that it can also be a symptom. Is that accurate?

[midoamy]

I thought of another question. Stewart was fully vaccinated just before being diagnosed. All my dogs have been vaccinated and I only do Heartworm treatment in the warm months plus a three year rabies shot. Given the shelf life of pet vaccines, I don't believe in redoing the other vaccines. My question is regarding heartworm treatment...could that be a trigger? Could the Rabies vaccine be one as well? What is the take on that from vets well versed in AI disorders?

[Jo CIMDA]

Hi

As far as I am aware myositis is a specific disease and not just a symptom. Anyway, I haven't seen any evidence to suggest it is a symptom.   

It is known to occur in large breeds which fits in with Stewart. It is a disease that can be primary, and therefore manifests alone, or as you know can be associated with various cancers.  It is also an AI disease that can occur simultaneously with other AI diseases such as polyarthritis and dermatomyositis (myositis and dermatitis), and of course with SLE.  When my boy was finally diagnosed and treated the specialist said he had everything wrong with him, MMM, Polymyositis, IM Vasculitis, IMHA etc........ 

I referenced Michael J Day's book for you, Clinical Immunology of the dog and Cat, Second edition,  and this I thought was interesting. It may or may not be relevant to Stewart.   There is a recognised myositis called:

Extraocular Myositis

'In this form of myositis, clinical signs (bilateral exophthalmos related to muscle swelling) are related to the Extraocular muscles, with sparing of masticatory and limb musculature.  There are no antibodies to type 2M fibres, so the immune response may involve a target antigen unique to this muscle group.  Golden retrievers may be predisposed to EOM.  CK (Creatine Kinase) may be mildly elevated and muscle biopsy should reveal mononuclear inflammatory infiltration restricted to the Extraocular muscles. Therapy is as described  for the other forms of myositis'.



As for heartworm treatment and vaccinations:  When I attended a seminar at the Royal Veterinary College, by Prof Catchpole, I asked if a dog that has had an AI disease should ever be vaccinated again, or spot on treatment used, and he said, "No".   He continued to say that the benefits have to outweigh the risks and in a dog that is genetically predisposed to autoimmunity the risks are too high.   This is because vaccination and other chemicals, drugs, stressful situations etc., are all potential triggers for AI disease. These potential triggers should be limited in all dogs, but more so in a dog known to be predisposed to AI disease.

Some years ago I was invited to attend a small meeting of top UK veterinary clinicians and I sat next to an orthopaedic specialist (a professor who worked at one of the vet colleges, and has written several orthopaedic veterinary manuals) he told me that within the synovial fluid of dogs with immune mediated polyarthritis he has found the distemper virus and he said there was only on way of that getting into the joints and that was through vaccination.  What an honest guy!

Vaccinating and using preventative treatments etc.,  has to be the decision of the owner, and you must feel comfortable about that decision.  The best thing is to do as much research as possible and make an informed decision.   There are no guarantees but if you limit the triggers then you reduce the chance of a relapse.   

More on vaccination can be found at   http://www.wsava.org/guidelines/vaccination-guidelines    . Guidelines may vary from one country to the other.

Jo

[midoamy]

Thank you so much for all the information. I really appreciate it. I will keep you posted with any developments.