Myositis and myopathiesHave recent immunogenetic investigations increased our understanding of disease mechanisms in the idiopathic inflammatory myopathies?Chinoy, Hector; Ollier, William E.R; Cooper, Robert G Author Information Rheumatic Diseases Centre, Hope Hospital, Salford, UK Correspondence to Robert G. Cooper, Rheumatic Diseases Centre, Hope Hospital, Salford M6 8HD, UK Tel: +44 (0)161 206 4367; e-mail: [email protected] Current Opinion in Rheumatology: November 2004 - Volume 16 - Issue 6 - p 707-713 doi: 10.1097/01.bor.0000142339.24380.b7 Buy Metrics Abstract Purpose of review The idiopathic inflammatory myopathies (IIM) continue to provide a challenge given the variable effectiveness of the available treatments, and immunogenetic studies are ongoing to further elucidate IIM disease mechanisms. This review examines how recent research has improved our understanding of the mechanisms that lead to IIM. Recent findings HLA-DRB1 studies in a large homogenous cohort of UK Caucasian patients have confirmed that polymyositis (PM) and dermatomyositis (DM) are not genetically identical diseases while other studies have shown that tumor necrosis factor alpha is genetically implicated in disease susceptibility. Some remarkable results from an international collaboration, correlating gene-environment interactions, clearly suggest that ultraviolet light is capable of modulating both clinical and immunologic features of IIMs. Studies on microchimerism are unraveling interesting associations in juvenile DM patients, and bolstering the hypothesis that myositis may be an ‘allo-immune’ disease. mRNA gene expression profiling is helping to increase our understanding of myositis pathogenesis, whilst animal models have provided new information on the roles of Th1 responses and nitric oxide synthase in muscle disease. New candidate genes have been examined in inclusion body myositis (IBM), and a novel gene transfer experiment has been conducted, which led to significant changes in expression of the IBM phenotype. Summary Improving the understanding of the immunogenetics and immunopathogenesis of the IIMs may in the future provide novel therapeutic targets, and thus improve outcomes in these difficult diseases. © 2004 Lippincott Williams & Wilkins, Inc.