TRIM21 and systemic sclerosis: Currently, autoantibodies have been identified in studies as specific serological biomarkers for SSc diagnosis and prognosis, including anti-centromere, anti-topoisomerase I (anti-Topo I), anti-RNA polymerase III, and two major types of SSA/Ro antibodies, anti-Ro60 and anti-TRIM21, which co-exist with them (115).