Overview of Myositis
The inflammation and swelling of muscles is termed as myositis. Common signs of myositis include swelling, pain and weakness. Inflammation of muscles can be caused by variety of factors such as autoimmune diseases, viral or bacterial infections, physical injury and medicinal drugs. Different types of myositis are inflammatory myositis, dermatomyositis, inclusion body myositis and pyomyositis.
Causes and Risk Factors of Myositis
Myositis can be caused by any condition that induces muscle inflammation; these conditions can be grouped as autoimmune diseases, microbial infections, drugs and physical injuries. Autoimmune response in body can be induced by viral attack such as retroviruses or cancer. Body’s immune system attacks muscles and causes their inflammation and damage; a condition known as inflammatory myositis. Polymyositis, dermatomyositis, inclusion bodies myositis and juvenile myositis are examples of inflammatory myositis. Other autoimmune diseases such as lupus, rheumatoid arthritis and scleroderma tend to cause milder forms of myositis. Viruses such as HIV, influenza, echoviruses, coxsackievirus and Human T-Lymphotropic Virus 1 (HTLV_1) are implicated in the pathogenesis of myositis via direct invasion or autoimmune response. Different bacterial species can also cause myositis such as Staphylococcus aureus is causative agent of pyomyositis or myositis tropicans while spirochete Borrelia burgdorferi also cause muscle inflammation in lyme disease. Several drugs such as lipid lowering statins and fibrates, colchicine and alpha-interferon are also known to induce muscle inflammation also called as toxic myopathies. Severe exercise and injuries can also result in muscle pain, swelling and weakness for hours to several days.
Signs and Symptoms of Myositis
The common sign of myositis is muscle weakness, but people may also have muscle pain (myalgia), fatigue, difficulty in moving limbs, risk of falls and troubled swallowing or breathing. Polymyositis is characterized by flares, muscle weakness (especially in shoulders, thighs and hips), lung issues, fever, weight loss, Raynaud’s phenomenon (bluish discoloration and coldness of fingers and toes) and joint pain. Dermatomyositis is manifested by a skin rash, muscle weakness, patchy purple or red rashes on the eyelids or knuckles, elbows, knees and toes. Rashes can appear on the face, neck, chest and back. People may also undergo weight loss, fever, lung issues and photophobia.