TRIM21 and systemic sclerosis: Of 100 patients, 53 were single positivity for any autoantibodies and 48 of which were classic SSc‐specific autoantibodies (26 with anti‐Scl70 ab, 16 with ACA, 6 with anti‐RNAPIII ab), and 5 were SSc‐associated autoantibodies (1 with anti‐Ku ab, 1 with anti‐PM/Scl100 ab, 2 with anti‐PM/Scl75 ab, and 1 with anti‐Ro52 ab).