Inflammatory Myopathies

Idiopathic inflammatory myopathies are relatively rare diseases. Polymyositis and dermatomyositis are more common in women than men (2:1 ratio), while inclusion body myositis is twice as common in men. Inflammatory myopathies are a heterogeneous group of chronic systemic autoimmune diseases with an annual incidence of two to five cases per million, characterized by muscle inflammation and progressive muscle weakness. There are three major diseases which includes Dermatomyositis (DM) including a distinct juvenile subtype (JDM), Polymyositis (PM), and Inclusion Body Myositis. DM is a compliment mediated microangiopathy affecting skin and muscle. PM and IBM are T-cell mediated disorders, where CD8 positive cytotoxic T cells invade muscle fibers expressing MHC class I antigens, this leading to fiber necrosis. In IBM, vacuolar formation with amyloid deposits are also present. This article summarizes the clinical, histochemical and immunological features as well as the treatment options of the inflammatory myopathies.