Global cell infiltration in PsA and RA synovitis in the histologic analysis is similar, although characterization by immunohistochemistry of the infiltrating cells could encounter differences, as synovial infiltration by mast cells, CD15+ neutrophils and CD163+ macrophages is increased in SpA, included PsA, compared with in RA (7). Here, FUT4 is linked to rheumatoid arthritis.