TRIM21 and myositis disease: If EMG/ ENG and/or musculoskeletal MR are compatible with SIAM, the next step consists of the analysis of autoantibodies patterns, including the extended myositis panel (anti-Mi2/alpha and beta, anti-DNA, Ku, SRP, PL7, PL-12, EJ, OJ, Jo 1, PM-Scl100 and PM-Sc75, Ro-52, NXP2, TIF 1g, SAE1 and MDA5) and anti-HMGCR Ab, necessary to make a differential diagnosis between SIAM and other forms of autoimmune myositis [24].