Masticatory Myositis in Dogs: Ginger’s Painful Mouth
Masticatory myositis is an auto-immune disease. In other words, the immune system attacks the dog’s own jaw muscles as a foreign invader.
As a result, the puppies are in severe pain and unable to open their mouth. Can you imagine if it hurt when you tried to eat? And I mean really hurt.
Some breeds, including Cavalier King Charles Spaniel, carry a genetic predisposition to this condition. However, auto-immune diseases require two things:
- a genetic predisposition
- and a trigger
The trigger, though, can be many things, including:
- infections bacterial or viral
- vaccinations
- environmental toxins
- allergens
- adverse reactions to medication
- even stress

Other predisposed breeds:
- German Shepherds
- Labrador Retrievers
- Golder Retrievers
- Doberman Pinschers
Source: VCA Hospitals
Ginger’s story
You know how adorable Cavalier King Charles Spaniel puppies are. Ginger was no exception. Ginger was a happy girl. She played and enjoyed being loved with all her might.
Feeding was one of the highlights of her day.
It took all but twelve hours for all that to change.
Ginger’s symptoms
Ginger’s turn from a normal puppy to a dull, quiet and withdrawn happened fast. She didn’t want to eat and when anybody tried to touch her head she’d back away and yelp. Something was obviously wrong.
Veterinary exam
Quickly, Ginger’s parents took her to a veterinarian.
The most likely causes behind mouth pain in dogs are dental issues or foreign bodies. Ginger was only three months old. Could she have something stuck in her mouth? Could it be a stick injury?
Unfortunately, Ginger would let the veterinarian get anywhere close to her head at all. The only way to examine her mouth was giving her general anesthetic.
Diagnosing Ginger
To the veterinarian’s surprise, he was unable to open Ginger’s mouth even under anesthesia. What gives?
Follow-up x-rays didn’t offer any answers. Everything looked normal.
Symptoms of masticatory myositis in dogs include:
- inability to open mouth
- inability to eat
- swollen masticatory muscles
- severe facial pain
However, the only way to definitely diagnose masticatory myositis in dogs has been a biopsy. Fortunately, there is now a blood test that can measure the antibodies attacking the muscles too.
Diagnosing conditions so rare that you hardly hear about them is always a challenge.
Pain relief
The first thing Ginger’s veterinarian did was to take care of her terrible pain. Ginger’s parents brought her home with strong pain medications. Likewise, they also received recommendations for soft moist food. Finally, the poor girl could get some nourishment into her.
The pain meds did make Ginger feel much better and she started eating.
Complications
Unfortunately, all the medication upset her digestive system. The only option was to stop all medication. That, however, brought the pain back.
It became a matter of finding a middle ground between
- controlling Ginger’s pain
- while minimizing the risk of damaging her GI system
In the meantime, her veterinarian kept working on the diagnosis. All this happened before the blood test to diagnosis masticatory myositis in dogs became available.
Blood tests, just as the x-rays, didn’t show anything useful. Everything looked normal.
Thinking out of the box
Could something such as electromyography (EMG) provide needed answers? It would be a non-invasive way of figuring out what was going on with Ginger’s chewing muscles. It is not a veterinary test but maybe they could pull it off.
Then, Ginger’s veterinarian found a freshly-published report about masticatory myositis in Cavalier King Charles Spaniels. Finally, there was the answer to Ginger’s severe jaw pain. Her veterinarian worked with San Diego laboratory to confirm Ginger’s diagnosis.
Treating Ginger
As soon as Ginger received treatment with immunosuppressive medications, she felt immediately better.
As a fallout of her illness, Ginger still has some residual problems. But she is feeling good and continue to enjoy her life.
Ginger’s story took place in 2013. Today, diagnosing her would have been easier. Treatment options, however, haven’t changed much.
I decided to feature this older story to highlight the dedication and persistence of her veterinarian. He didn’t stop until he got to the bottom of it. Which is what makes a good veterinarian. No, that is what makes a great veterinarian.
Source story:
Ginger, a three-month-old Cavalier King Charles Spaniel puppy who had a very painful mouth
Further reading:
Masticatory Myositis in Dogs – When Chewing Hurts!