According to a systematic review RCTs found retinoids to be moderately effective as monotherapy at doses of 75 mg/day or 1 mg/ kg/day. Acitretin was as effective as etretinate, which was less effective than cyclosporin. There is good RCT evidence to support the use of combination treatment with a retinoid and psoralen plus ultraviolet A (PUVA). This combination was more effective than retinoid therapy alone and had the advantage of lowering the cumulative ultraviolet A (UVA) dose.