TRIM21 and dermatomyositis: Autoantibodies in DM are now categorized into two groups: (1) myositis-specific autoantibodies which include Jo-1, PL-7, PL-12, OJ, Mi-2, and signal-recognition particle; (2) myositis-associated autoantibodies such as PM/Scl, Ro/SSA, and U1RNP.