TNF and psoriasis: Regarding the etiopathogenesis, although incompletely elucidated, a multifactorial and polygenic pattern of psoriasis that includes the presence of a number of susceptibility genes (PSORS 1-9) involved [2] has been described and also some disease-related genetic variations associated with tumor necrosis factor TNF- α, p40 subunit of interleukins 12/23 and IL 23 receptor.