Eosinophilic Myositis (Masticatory Muscle Inflammation) in Dogs
- Synonyms: Myositis eosinophilica, Masticatory muscle myositis
- Occurrence: very rare
- Location of disease: Head/Neck
When to visit the vet?
Urgent see a veterinarian within 24 hours
If the condition worsens / symptoms persist, consult a veterinarian.
Definition
Eosinophilic Myositis, also known as Masticatory Muscle Inflammation, is an inflammatory disease of the chewing muscles in dogs, characterized by an abnormal accumulation of eosinophilic cells, a type of white blood cell. This disease leads to Pain, Swelling, and loss of function of the affected muscles.
The most important facts at a glance
Eosinophilic Myositis, also known as Masticatory Muscle Inflammation, is an autoimmune disease in dogs in which the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. mistakenly attacks the chewing muscles, especially the temporalis and masseter muscles. This inflammation is caused by eosinophilic granulocytesEosinophilic granulocytes are a type of white blood cell that plays an important role in the immune response, especially in allergic reactions and parasitic infestations. An increased number of these cells in the blood may indicate allergic diseases or parasitic infections in dogs and cats., a type of Immunzellen. Although the exact causes are unknown, genetic predispositions, environmental factors, and infections may play a role. Certain dog breeds, such as the German Shepherd and the Golden Retriever, show a higher susceptibility. Symptoms include exophthalmos, Masseter muscle swelling, Difficulty eating and Schmerzen when opening the jaw. The DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made through clinical examinations, Blutuntersuchung and imaging procedures. A muscle biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions. can provide a definitive DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. The Therapie aims to reduce inflammation and restore muscle activity, usually through Kortikosteroide. An acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. may require high-dose Steroide, followed by a gradual reduction in dose. Long-term maintenance therapies may be necessary to prevent relapses. The Prognose is good with early DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment, but left untreated, the disease can lead to permanent muscle changes. Preventive measures are difficult because the causes are not fully understood. However, a balanced diet and regular veterinary check-ups are helpful to promote the dog’s health.
Causes
Masticatory muscle myositis is an autoimmune disease in which the body’s own immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. mistakenly attacks the muscle fibers responsible for chewing. These muscles predominantly include the temporalis and masseter muscles. The inflammation is caused by an InfiltrationInfiltration refers to the penetration or accumulation of cells or fluids in a tissue or area that is normally free of them. This can occur as part of inflammatory reactions, Tumors, or other pathological processes. of eosinophilic granulocytesEosinophilic granulocytes are a type of white blood cell that plays an important role in the immune response, especially in allergic reactions and parasitic infestations. An increased number of these cells in the blood may indicate allergic diseases or parasitic infections in dogs and cats., a specific type of Immunzellen.
The exact causes of Eosinophilic Myositis are not fully understood, but it is believed that genetic predispositions, environmental factors, and possibly infections could play a role. In some dog breeds, such as the German Shepherd and the Golden Retriever, there appears to be a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. that increases the risk of developing this disease.
Another possible factor could be a reaction to certain medications or vaccines that affect the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body.. However, these connections have not been clearly proven and require further research to fully understand them.
Symptoms
The symptoms of Eosinophilic Myositis are often sudden and severe. One of the most common signs is Masseter muscle swelling, which prevents the dog from fully opening its mouth. This can lead to Difficulty eating and drinking, which is sometimes referred to as “trismus.”
In addition, affected dogs may show Pain in the jaw muscles and exhibit Sensitivity to touch. In some cases, Weight loss may also occur because the dog eats less due to the Pain.
Another common symptom is Fever, which is triggered by the inflammatory response in the body. Some dogs also show general signs of discomfort, such as lethargy and decreased activity.
Diagnosis
The DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of Eosinophilic Myositis is usually made through a combination of clinical examination, Blutuntersuchung and imaging procedures. During the clinical examination, the veterinarian checks the chewing muscles for Swelling and Schmerzen. A complete blood count may show an increased number of eosinophilic granulocytesEosinophilic granulocytes are a type of white blood cell that plays an important role in the immune response, especially in allergic reactions and parasitic infestations. An increased number of these cells in the blood may indicate allergic diseases or parasitic infections in dogs and cats., indicating an inflammatory response.
A definitive DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. can be made by a muscle biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions., in which a sample of the affected muscle is taken and examined histopathologisch. This examination typically shows an InfiltrationInfiltration refers to the penetration or accumulation of cells or fluids in a tissue or area that is normally free of them. This can occur as part of inflammatory reactions, Tumors, or other pathological processes. of eosinophilic cells and other inflammatory changes in the muscle fibers.
In some cases, imaging techniques such as Ultraschall or MRI can also be used to assess the extent of the inflammation and possible Muskelatrophie. These methods help to rule out other possible causes for the symptoms.
Therapy
The treatment of Eosinophilic Myositis aims to reduce inflammation and restore muscle activity. This is mainly achieved through the administration of immunosuppressiveImmunosuppressive agents are medications or substances that specifically suppress the activity of the immune system. They are used in dogs and cats to treat autoimmune diseases, allergies, and to prevent rejection reactions after transplants. drugs such as Kortikosteroide. These medications work by suppressing the activity of the immune system, thereby reducing the inflammatory response.
In acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. cases, a high-dose Steroidtherapie may be necessary to quickly control the symptoms. Once the symptoms have subsided, the dose is gradually reduced to minimize side effects. Long-term, a low-dose maintenance therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. may be necessary to prevent relapses.
In addition to drug therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions., supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. care, such as special diets or nutritional supplements, can be helpful to improve nutrient absorptionAbsorption refers to the uptake of substances by living cells or tissues. In the context of veterinary medicine, it often refers to the absorption of nutrients, drugs, or toxins from the digestive tract into the bloodstream. and support the healing process.
Prognosis and follow-up care
The Prognose for dogs with Eosinophilic Myositis varies depending on the severity of the disease and the response to treatment. With early DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and appropriate Therapie, many dogs have a good Prognose and can lead a relatively normal life.
However, some dogs are at risk of relapse, especially if treatment is stopped too early or the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. is reactivated. In such cases, long-term maintenance therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. may be necessary to keep the disease under control.
Left untreated, Eosinophilic Myositis can lead to permanent muscle changes and loss of function, which significantly limits the quality of life of the affected dog.
Prevention
Since the exact causes of Eosinophilic Myositis are not yet fully understood, there are no specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. measures. However, some general measures can help to reduce the risk of disease.
A balanced diet and regular veterinary check-ups are important to promote the dog’s general health and detect potential problems early. In addition, Kontakt with potential triggers of autoimmune reactions, such as certain medications or vaccines, should be discussed with the veterinarian.
In dogs that are genetically predisposed, regular check-ups can help to detect signs of the disease early and start treatment quickly.
Outlook on current research
Outlook on research into Eosinophilic Myositis (Masticatory Muscle Myositis)
Eosinophilic Myositis or Masticatory Muscle Myositis (MMM) is now understood as a targeted autoimmune disease against 2M muscle fibers of the chewing muscles. Basic research focuses on which Immunzellen and signaling pathways (B cells, T cells, cytokines) drive autoantibody formation and chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. inflammation and why certain breeds (e.g. German Shepherd, Weimaraner) are particularly affected.
Diagnostically, the 2M antibodyAn antibody is a protein produced by the immune system to recognize and bind specific antigens. By binding to the antigen, antibodies can help destroy or neutralize it. test remains a key tool, but is not perfect: antibodyAn antibody is a protein produced by the immune system to recognize and bind specific antigens. By binding to the antigen, antibodies can help destroy or neutralize it. titers do not always correlate cleanly with clinical activity. Therefore, imaging and functional markers (e.g. CT/MRI of the chewing muscles, Ultraschall, measurement of the mouth opening angle) are systematically investigated to enable earlier DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and better therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. follow-up.
Therapeutically, the focus is shifting away from pure high-dose cortisone therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. towards individual, lower-side-effect Immunsuppression protocols (e.g. combination with cyclosporine, mycophenolate, leflunomide). A recent report describes the use of a selective JAK-1 inhibitor (oclacitinib) with clinical improvement with reduced steroid load – an indicationIndication refers to a valid reason or rationale for using a specific treatment, medication, or medical procedure. It is based on the diagnosis and the patient's clinical condition. of future targeted immunomodulation instead of broad Immunsuppression.
In the future, genetic risk profiles, refined autoantibody tests and standardized outcome measures (mouth opening angle, muscle volume, quality of life) are expected to be combined to better predict relapses and adapt therapies early and precisely. Overall, the development is clearly moving towards earlier, precise diagnostics and tailored, steroid-sparing therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions..
Frequently asked questions (FAQs)
1. What is Eosinophilic Myositis in dogs?
2. Is that the same as Masticatory Muscle Myositis?
3. Which dogs are particularly affected?
4. What are the signs of the disease?
5. Is the disease painful?
6. How is the Diagnosis made?
7. How is it treated?
8. Are there new therapy approaches?
9. What is the Prognose?
10. Does the disease come back?
Literature
Selva-O’Callaghan, A., Trallero-Araguás, E., & Grau, J. M. (2014). Eosinophilic myositis: an updated review. Autoimmunity Reviews, 13(4-5), 375-378.
Reiter, A. M., & Schwarz, T. (2007). Computed tomographic appearance of masticatory myositis in dogs: 7 cases (1999–2006). Journal of the American Veterinary Medical Association, 231(6), 924-930.