Myositis is the inflammation and deterioration of skeletal muscle tissue. The inflammation can affect just one muscle or it can affect a group of muscles. Dogs can be affected by several different types of myositis. They all require veterinary treatment. Each type requires a different type of treatment.
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Types
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According to the ninth edition of "The Merck Veterinary Manua,l" dogs can suffer from three common types of myositis: myositis ossificans, polymyositis and masticatory myositis. Masticatory myositis is also known as eosinophilic myositis. Each type affects different muscle and tissue groups in the dog's body. The myositis ossificans affects the muscles and tissues around the hip joints. Polymyositis affects the whole muscular system. Masticatory myositis affects the muscles involved in chewing. Other types of myositis each have their own unique name.
Myositis has no known cause. It is often a symptom of other illnesses.
Identification
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Depending on the areas affected, the identifying symptoms will vary. For myositis ossificans, symptoms are increasing pain around the hip area and the gradual loss of hip movement as the condition worsens. For polymyositis, symptoms include a stiff gait, muscle pain, lethargy, and muscle atrophy. For masticatory myositis, symptoms include swollen jaw muscles, difficulty opening the jaw, and anorexia for chronic cases.
A veterinarian needs to accurately diagnose the type of myositis before any treatment is attempted. The vet may use electromyography to determine the location of affected muscles. He may also perform a muscle biopsy to determine the stage of the muscle deterioration.
Treatment
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Treatment for various types of myositis can differ. Oral corticosteroids are the preferred type of drugs for treating polymyositis and masticatory myositis. A veterinarian may, however, prescribe other immunosuppressive agents to treat polymyositis. Surgical resection is the only treatment available for myositis ossificans.
Results after treatment are good for all three types. But relapses typically occur for polymyositis and masticatory myositis. If relapses occur often, full recovery may not be possible.
Causes
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Although there is no known cause for myositis, other illnesses can produce myositis as a symptom. "The Merck Veterinary Manual" mentions a link between myositis ossificans and von Willebrand's disease, a bleeding disorder. As well, polymyositis may be linked with megaesophagus and immune-mediated disorders. Masticatory myositis has not been linked with any particular illness, but tests will show the dog's autoantibodies attacking the muscle tissues of the jaw.
Considerations
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If you are given corticosteroids for your dog's treatment, do not expose the dog to other sick dogs. Your dog's immune system will be suppressed during treatment and will not be able to ward off illness as well as before.
Myositis can be a symptom of an underlying problem. If left to progress, it can become fatal.
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