IL17F and psoriasis: Both of them have been frequently associated with many inflammatory diseases, including psoriasis.23, 24, 25 Although IL-17A appears to play a central role in the pathogenesis of psoriasis, recent studies have reported an increasing level of IL-17F in lesional skin in psoriasis, in addition to the demonstration that IL-17F has similar functions as IL-17A and IL-17F has begun to focus on its possible critical role in the immunopathogenesis of the disease.26