We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Pets

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What is Masticatory Muscle Myositis?

By Soo Owens
Updated: Jun 04, 2024
Views: 13,651
Share

Masticatory muscle myositis (MMM) is a muscle disease that causes inflammation in the masticatory muscles, the muscles used for chewing, in dogs. Symptoms usually include jaw pain, excessive drooling and swelling of the jaw muscles. Chronic MMM can lead to an inability to open and close the mouth, called trismus. It is the most common type of myopathy, or muscular disease, to afflict dogs.

MMM is an autoimmune disorder in which the immune system targets the lower jaw muscle. This is because of the presence of certain fibers in the masticatory muscles that are absent from the rest of the body. These masticatory muscle (2M) fibers resemble the protein structures of certain bacteria, causing the animal's immune system to target those fibers as foreign bodies and attack them. This process causes inflammation of the muscles and, if it is chronic, atrophy of the involved muscles.

There are two types of masticatory muscle myositis: acute and chronic. The signs for each can vary, with the chronic form being the most common of the two. Acute MMM usually involves pain and masticatory muscle swelling as well as a fever and enlarged mandibular lymph nodes. Exophthalmus, known as protruding eyeballs, and blindness from optic nerve compression also can occur. Chronic MMM might contain any of the aforementioned symptoms but can also exhibit recurring inflammation and even atrophy of the mastication muscles.

Larger dog breeds comprise most cases of masticatory muscle myositis. German shepherds, Cavalier King Charles spaniels, Doberman pinschers and retrievers can be more susceptible to the disease, though it can occur in any breed. Most reported incidents involve young or middle-aged dogs.

Diagnosis of masticatory muscle myositis is done via a 2M antibody assay or a masticatory muscle biopsy. A false negative is possible from a 2M antibody test if the disease has already caused the destruction of the 2M fibers and led to severe atrophy. Thus, an animal that has received a negative result from a 2M antibody test but continues to exhibit signs of MMM still retains a 15 percent chance of having masticatory muscle myositis.

Corticosteroids over a four- to six-month period are the usual method of treatment for MMM. The medicine is administered in decreasing doses over the treatment period. This typically results in restored function, though the extent of this function is dictated by the amount of atrophy and muscle damage already present. It is possible for MMM to recur even after treatment has ended and the animal has appeared to have been healed.

Share
All Things Nature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
Share
https://www.allthingsnature.org/what-is-masticatory-muscle-myositis.htm
Copy this link
All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.

All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.