PPI networks selected five hub genes, which have pivotal roles in psoriasis: peptidylprolyl isomerase F (PPIF), superoxide dismutase 2 (SOD2), glycogen synthase 1 (GYS1), adenosylhomocysteinase (AHCY) and phosphogluconate dehydrogenase (PGD) (The details of the hub genes were represented in Table 1). The gene discussed is PGD; the disease is psoriasis.