Eosinophilic Myositis (Masticatory Muscle Inflammation) in Dogs
- Occurrence: very rare
- Location of illness: Head/Neck
Eosinophilic myositis, also known as masticatory muscle inflammation, is an inflammatory disease of the masticatory 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 masticatory 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 immune cell. 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 drinking, and Pain when opening the jaw. 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, blood tests, 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.. Treatment aims to reduce inflammation and restore muscle activity, usually with corticosteroidsCorticosteroids are a class of steroid hormones that occur naturally in the body and can also be produced synthetically. They have anti-inflammatory and immunosuppressive properties and are used in veterinary medicine to treat a variety of conditions.. 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 steroidsSteroids are a group of lipids that include both hormones and certain medications. In veterinary medicine, steroids are used to treat inflammatory conditions, allergies, and autoimmune diseases in dogs and cats., followed by a gradual reduction in dose. Long-term maintenance therapies may be necessary to prevent relapses. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. 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 primarily include the temporalis and masseter muscles. The inflammation is caused by an infiltration 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 immune cell.
The exact causes of eosinophilic myositis are not fully understood, but genetic predispositions, environmental factors, and possibly infections are believed to 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 associations have not been clearly proven and require further research to fully understand them.
Symptoms
The symptoms of eosinophilic myositis are often sudden and severe. The most common signs include swelling of the masticatory muscles, which prevents the dog from fully opening its mouth. This can lead to Difficulty eating and drinking, 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, blood tests, and imaging procedures. During the clinical examination, the veterinarian checks the masticatory muscles for swelling and pain. 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 histopathologically. 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 ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. or MRI can also be used to assess the extent of the inflammation and possible muscle atrophyMuscle atrophy is the loss of muscle mass that can be caused by inactivity, malnutrition, or certain diseases. In dogs and cats, muscle atrophy can occur due to chronic diseases, aging, or after prolonged immobilization.. 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 by administering 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 corticosteroidsCorticosteroids are a class of steroid hormones that occur naturally in the body and can also be produced synthetically. They have anti-inflammatory and immunosuppressive properties and are used in veterinary medicine to treat a variety of conditions.. These drugs work by suppressing the activity of 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., thereby reducing the inflammatory response.
In acute cases, high-dose steroid therapySteroid therapy is the medical treatment using steroidal medications. It is used in dogs and cats to reduce Inflammatory conditions, treat immune-mediated diseases, and to provide support during certain cancer treatments. may be necessary to quickly control 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 prognosis for dogs with eosinophilic myositis varies depending on the severity of the disease and the response to treatment. With early diagnosis and appropriate 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., many dogs have a good prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. 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 reduce the risk of disease.
A balanced diet and regular veterinary check-ups are important to promote the dog’s overall health and detect potential problems early. In addition, contact 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.
When to visit the vet?
Urgent see a veterinarian within 24 hours
If the condition worsens / symptoms persist, consult a veterinarian.