According to individual disease, Ab reactivity against fragments Ro52-1, Ro52-4, and Ro52-5 were as follows (SjS and SLE are grouped together as their reactivities to different Ro52 fragments were similar): Abs against Ro52-1 were less frequent in SSc than in SjS/SLE (5/43 [11.6%] vs. 20/48 [41.7%], p = 0.001); Abs against Ro52-4 were less frequent in SSc than in SjS/SLE (12/43 [27.9%] vs. 24/48 [50%], p = 0.03). This evidence concerns the gene TRIM21 and systemic lupus erythematosus.