These pro-inflammatory molecules (IL-1b, IL-6, TNF-a, Leptin, IL-12, IL-23) pass into the bloodstream stimulating inflammation in multiple tissues, including the skin, and represent a biologically plausible explanation for the relationship between obesity and psoriasis both in its onset and perpetuation [92,93]. The gene discussed is IL23A; the disease is obesity due to melanocortin 4 receptor deficiency.