The ethology of PN remains unknown, but current research suggests that its pathogenesis is related to neurological factors (increased expression of substance P and calcitonin gene-related peptide), immune factors (include Th2, Th1, Th-22, IL-17, IL-31), infectious factors, psychosomatic factors and tumor factors [7–9]. Here, IL17A is linked to poikiloderma with neutropenia.