ERAP1 and rheumatoid arthritis: The analysis of RA patients according to the severity of the disease and DAS28 (Disease Activity Score 28) showed differences between patient subgroups in the ERAP1 rs26653 G > C SNP (p = 0.043/pcorr.= ns) and ERAP2 rs2248374 G > A (p = 0.003) (Table 4).