PADI4 and rheumatoid arthritis: Furthermore, seven haplotypes in PADI4 were found in the RA-ILD vs. RA comparison; the ACTC haplotype is associated with ILD susceptibility in RA patients (OR = 2.64, 95% CI = 1.01–6.88, p = 0.038), which has a high linkage disequilibrium (r2 value ≥ 80), shown in Table 5 and Figure 2b.