AKR1C3 and psoriasis: One of the key genes in the top unique SP vs C pathways was AKR1C3. Aldo-keto reductase 1C3 (AKR1C3) is a gene that is expressed in the epidermis that mediates the metabolism of steroid hormones and has been shown to affect keratinocyte differentiation and is up-regulated in atopic dermatitis25 but not in psoriasis.