Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases with shared proximal muscle weakness and inflammation. Muscle involvement is typically symmetric, proximal and can be present very mild to very sever. IIMs are categorized to dermatomyositis (DM), polymyositis (PM), inclusion body myopathy and immune- mediated necrotizing myopathy (IMNM). Electromyography, MRI and muscle biopsy are valuable methods to differentiate myopathies. Muscle biopsy is critical for the diagnosis of the different forms of IIM. In this regard, the presence of perifascicular atrophy is strongly suggestive of DM, whereas the finding of rimmed vacuoles in the appropriate context suggests IBM. Besides these, the presence of autoantibodies and elevated muscle enzymes is helpful in the diagnosis of myositis. The known autoantibodies are of most important in the context of myositis include anti-Jo-1, anti- SRP (signal recognition particle), anti- HMGCR (3- hydroxyl-3-methyl-glutaryl coenzyme A r