Pictures Of Dogs With Masticatory Muscle Myositis

Who develops MMM? Are there some breeds that are more susceptible to MMM than others?

MMM can occur in any breed and in both males and females. The average age of MMM patients is 3 years, but there have been cases of dogs as young as 4 months with the disease. There are several breeds that are identified as more likely to develop MMM, These breeds include:

  • Golden Retrievers
  • Doberman Pinschers
  • German Shepherds
  • Labrador Retrievers
  • Cavalier King Charles Spaniels
  • Rottweilers
  • Weimaraners
  • Large Breed Dogs
  • Symptoms of Masticatory Muscle Myositis in Dogs

    The symptoms of masticatory muscle myositis can vary depending on the muscles that are affected. If you notice any of these symptoms contact your veterinarian for an appointment to have a full assessment done on your dog.

  • Swelling of the muscles on the top of the head
  • Progressive muscle loss
  • Difficulty moving the jaw
  • Difficulty drinking
  • Difficulty eating or picking up food
  • Unable to open the mouth
  • Eyes look sunken
  • Eyes look protruding
  • Stiff movements
  • Weakness
  • Regurgitation of food and water
  • Difficulty swallowing
  • Difficulty breathing
  • Causes of Masticatory Muscle Myositis in Dogs

    Masticatory muscle myositis can be caused by several things.

    Infection or Virus

    Some form of an infectious agent, parasite or virus within the muscle can cause inflammation within the masticatory muscles.

    Abnormal Immune Reaction

    An abnormal immune reaction of the body against the muscle is known as immune-mediated myositis. The body produces antibodies that will target parts of the masticatory muscles. This will cause inflammation.


    Inflammation within the masticatory muscles can develop as pre-cancerous and then turn into cancer. Cancer found within the body can cause an immune reaction, causing masticatory muscle myositis. This is known as a paracancerous effect.


    Is masticatory myositis fatal in dogs?

    Masticatory myositis can be fatal as the dog cannot open its mouth to eat or drink properly. If the disease goes untreated or it has progressed to the point that most of the muscle fibers of the jaw have been replaced by fibrous tissue, this disease is not curable.

    How quickly does MMM progress in dogs?

    Masticatory Muscle Myositis initially causes swelling of the muscles on the top of the head followed, a week or two later, by progressive muscle wasting (loss of muscles). The dog usually has difficulty moving its jaw, which causes pain and problems when picking up food or drinking.

    How do I know if my dog has MMM?

    In the study, MMM generally carried a favorable prognosis when treated promptly with immunosuppressive doses of prednisone. Dogs typically regained normal masticatory function within 4 weeks of treatment, although 27% of affected dogs experienced relapse that resolved with continued glucocorticoid therapy.