Abstract
Polymyositis (PM) is an autoimmune disorder; result from abnormal activation of cytotoxic T lymphocytes (CD8 cells) and macrophages against muscular antigens as well as the strong extrafusal muscular expression of major histocompatibility complex class 1 causing damage to the endomysium of the skeletal muscles. Polymyositis develops over the months as compared to inclusion body myositis (IBM), which is a slowly progressive chronic myopathy developing in older individuals over a period of months to years with more severe symptoms. Many patients require treatment for many years. Polymyositis affects the distal musculature of the esophagus in the late stage of disease in up to 70% of the patients leading to the inability to swallow, as well as regurgitation problems that can cause aspiration pneumonia. The principal goals of therapy are to improve strength and improve physical functioning. Many patients require treatment for several years. The 5-year survival rate for treated patients is in the order of 95%. Up to one-third of PM patients may be left with some degree of residual muscle weakness.