Viral myositis is a rare complication of a viral infection that causes skeletal muscles to become inflamed, weakened, and painful. A person may have very isolated pain in a single muscle group, such as muscles around the hip or shoulder, or the condition can cause discomfort in many different places in the body at once. Symptoms tend to develop quickly, and an individual may find him or herself unable to even get out of bed in the later stages of viral myositis. Treatment typically consists of a course of antiviral drugs, fluids to prevent dehydration, steroids to reduce inflammation, and a long period of bed rest.
Muscle infection and inflammation are not common with most viral infections. Most cases of myositis are related to autoimmune conditions in which the immune system attacks healthy nerve and muscle fibers by mistake, acting as if they were dangerous pathogens. In the case of viral myositis, however, the immune system's attack is not misguided; viral pathogens really do pose a threat to the body. Human immunodeficiency virus (HIV) is the most common cause of myositis. Acute infections of coxsackievirus, influenza, and several other pathogens may lead to muscle inflammation as well.
A person who develops myositis is likely to experience pain, weakness, and swelling in one or more muscles. The quadriceps in the legs and lower back muscles are the most common sites. Inflammation can also affect the shoulders, arms, and neck. Myositis may be accompanied by more general symptoms of fever, fatigue, and full-body aches. In severe cases, the lungs, kidneys, or heart may be affected as well, leading to potentially life-threatening complications.
A doctor can diagnose viral myositis with a physical exam and blood tests. The physician asks about the patient's history and symptoms and examines different muscles to locate tender sites. Imaging tests such as ultrasounds and x-rays help to confirm swelling and inflammation in the muscles. Blood samples are screened for the presence of HIV or another virus that may be responsible for symptoms.
Treatment for myositis depends largely on the type of virus involved and the severity of symptoms. Patients with minor pain and low fevers are prescribed antiviral medications and instructed to get plenty of rest until symptoms resolve. If a person has significant discomfort, he or she may be hospitalized so that antivirals, fluids, and corticosteroids can be administered intravenously. HIV-positive individuals typically require more aggressive initial treatment and ongoing, lifelong medical therapy for their conditions. Most cases of viral myositis can be resolved or at least improved with careful treatment.