What Is Masticatory Myositis in Dogs?
Masticatory Muscle Myositis (MMM), or eosinophilic myositis, is an autoimmune disease where the body attacks the muscles of the head and jaw required for chewing (or mastication). Myositis means muscle inflammation (swelling).
This disease attacks the special fibers found only in the muscle of the head and jaw, and this extremely painful condition inflames muscles, preventing your dog from opening his or her mouth to eat, chew, or play with toys.
The disease affects the Type 2M muscle fibers, which are unique to the temporalis and masseter muscles of the head and jaw. There are acute and chronic forms of this disease which describe the progression of the disease. Dogs will progress from the acute to the chronic form of the disease over time, if untreated.
Both male and female adult dogs can be affected and are mostly young- to middle-aged dogs.
Most common breeds affected include:
Causes of Masticatory Myositis in Dogs
Most autoimmune diseases start for unknown reasons, but they can be due to parasitic or viral infections, vaccines or other reactions to medications, exposure to environmental toxins or allergens, stress, or an early sign of cancer. The cause of this disease is unknown, but there is an increase in the immunoglobulin G to the fiber protein myosin, a component in muscle.
Which Dog Breeds Are Predisposed to MMM?
It is important to remember that Masticatory Muscle Myositis can occur in any breed and gender. However, some dog breeds are genetically more predisposed to developing autoimmune reactions, including Masticatory muscle myositis. These breeds include:
Just because a dog breed is predisposed to developing genetic diseases does not mean it will automatically develop Masticatory Muscle Myositis or something similar. It is just essential to keep in mind if your dog ever starts displaying some of the symptoms mentioned above–and knowing when to consult a veterinarian.