In this review, we highlight the potential implications of dysregulation of the IL-23/IL-17 axis in chronic inflammatory skin diseases, including psoriasis, hidradenitis suppurativa (HS), atopic dermatitis (AD), alopecia areata (AA), pityriasis rubra pilaris (PRP), pemphigus, and systemic sclerosis (SSc). This evidence concerns the gene IL17A and familial pityriasis rubra pilaris.