However, the −794 CATT5–8 and −173 G>C MIF polymorphisms did not show significant differences with MIF serum levels in our study, results similar to those reported in Mexican Mestizo patients with RA [27], SLE [15], and psoriatic arthritis [28]; however, they were not able to replicate the association of MIF polymorphisms with MIF serum levels; this could be due to differences in the genetic structure of our population which may influence activity at the MIF gene locus. Here, MIF is linked to psoriatic arthritis.