Genetics of myositis - distinct backgrounds of subtypes.

Myositis is a heterogeneous group of inflammatory muscular disorders. Although the main etiology is autoimmune chronic inflammation, the underlying pathomechanism remains unclear. Advances in genetic technology have provided important insights into its complex pathophysiology. Large genetic studies on myositis have advocated a relationship with several HLA loci and possible disease susceptibility genes in non-HLA genes. Idiopathic inflammatory myopathy, or autoimmune myositis, was originally divided into polymyositis and dermatomyositis. However, this classification has recently been revised based on updated information on the pathophysiology of autoimmune myositis. Autoimmune myositis is currently understood to include at least four major clinicopathologically distinct entities: dermatomyositis, antisynthetase syndrome, inclusion body myositis, and immune-mediated necrotizing myopathy. This review aims to consolidate knowledge of the genetics of myositis in order to meet the current classification and highlights key findings for a more detailed understanding of the underlying pathomechanism.