TRIM21 and synovial sarcoma: To this end, we compared the clinical and immunological features of SS patients categorized into three serological subgroups: (1) positive for ANA, RF, anti-SSA/Ro and anti-SSB/La antibodies (quadruple-seropositive), (2) negative for ANA, RF, anti-SSA/Ro, and anti-SSB/La antibodies (quadruple-seronegative), and (3) positive for ANA and anti-SSA/Ro antibodies (double-seropositive).