Myopathies are a group of diseases involving inflammation and muscle weakness. There are three main types of inflammatory myopathy (when the disease becomes chronic): polymyositis, dermatomyositis and inclusion body myositis. Although there is no definite cause for the disease, it can have various causes, including exposure to toxic substances or drugs, diseases such as cancer or rheumatoid conditions, or viruses or other infectious agents. It is also believed to be an autoimmune disorder in which white blood cells affect blood vessels, muscle fibres and connective tissue in organs, bones and joints. The main symptoms appear with a slow but progressive muscle weakness that can also affect the arteries and blood vessels that traverse the muscle. The weakness may be accompanied by fatigue while walking, tripping over easily, fall and even difficulty swallowing or breathing. While these are chronic inflammatory diseases that have no cure, the symptoms can be alleviated. Some treatments include medication, physical therapy, exercise or heat therapy, among others.