In the pSS cohort, the levels of serum C3 and C4 in anti-Ro/SSA-positive were 1.02 (0.89–1.20) g/L and 0.18 (0.15–0.23) g/L, which were significantly lower than anti-Ro/SSA-negative patients (1.11 (0.96–1.22) g/L, p = 0.006; 0.20 (0.17–0.24) g/L, p = 0.004; respectively). Here, TRIM21 is linked to peeling skin syndrome.