RETINOIDS are synthetic and natural analogues of vitamin A that have various effects on cellular differentiation, cellular proliferation, immune system, and embryonic development. The present study reviews the history of systemic RETINOIDS in medicine, the structure of synthetic RETINOIDS and their mechanisms. The main focus is on their biologic functions, clinical uses, and the adverse effects of isotretinoin, acitretin, and bexarotene representing the most commonly used first, second, and third generation systemic RETINOIDS, respectively.

Background: Psoriasis treatment is very important regard to mental sequeler and creating orbidity. First line treatment of generalized plaque type psoriasis includes methotrexate,  phototherapy and RETINOIDS. Objective: To compare bath-PUVA and acitretin in the treatment of generalized plaque type psoriasis. Patients & Methods: 40 patients with generalized plaque type psoriasis with PASI scores of 15-20 in Razi Hospital in Tehran were randomly divided into 2 groups after giving consent. Each group included 20 patients. The first group was treated three times a week with bath-PUVA and the second group treated with acitretin 0.7 the efficacy of 2 treatments was mg/kg/day. The efficacy of 2 treatments regimens were determined and compared using PASI scores. Results: The clearance rate was 65% in bath-PUVA group and 75% in acitretin group. Patients in bath-PUVA needed 29 sessions and accumulative dose of 105.46 J/cm2 for clearance. Conclusion: Psoriasis patients responded to bath-PUVA treatment but this response required more sessions and higher total dose. The inherent differences and distinctive responses to light in the patients under study (in Iran) compared with patients with skin phototypes I, II might explain these differences.