Psoriasis is a chronic inflammatory disorder that is mediated by elements of the innate and
adaptive immune systems. Its characteristic features in the skin consist of inflammatory
changes in both dermis and epidermis, with abnormal keratinocyte differentiation and
proliferation. Despite the elucidation of many aspects of psoriasis pathogenesis, some
puzzling questions remain to be answered. A major question currently debated is whether
psoriasis is a primary abnormality of the epidermal keratinocyte or a reflection of …