The similarity of AD and RA pathomechanisms is visible in the activity of the immune system, which, under the influence of appropriate factors, produces inflammatory biomarkers (e.g., interleukin-6, interleukin-12, C-reactive protein, penxine 3, endotheline-1, resistin, and receptors for the end products of advanced glycation). Here, RETN is linked to rheumatoid arthritis.