Psoriasis, CD and UC share a number of genetic associations including interleukin family genes IL12B and IL23R, involved in cytokine-mediated immune response; STAT3, which is activated by the interleukin IL6 (also shared) to produce inflammatory T-cells (Yang et al., 2007); and (in psoriasis and UC) human leukocyte antigen HLA-B, which also plays an important role in the immune system. This evidence concerns the gene HLA-B and psoriasis.