Retinoids are structural and functional analogues of vitamin A that exert multiple effects on cellular differentiation and proliferation, the immune system, and embryonic development Retinoic acid receptors (RARs) and retinoid X receptors (RXRs) are ligand-dependent transcription factors belonging to the steroid–thyroid hormone nuclear receptor superfamily. Topical retinoids are used to treat acne, photoaging, psoriasis and a number of other conditions; the limiting factor is dose-related skin irritation, and teratogenicity risk is very low to non-existent. Oral retinoids are the most effective drugs available for severe acne (isotretinoin) and many disorders of cornification (acitretin and isotretinoin). They are also helpful in the management of psoriasis, especially pustular and erythrodermic forms (acitretin > isotretinoin), pityriasis rubra pilaris (acitretin and isotretinoin), cutaneous T-cell lymphoma (bexarotene) and chronic hand eczema (alitretinoin)