[Prescription of phototherapy in psoriasis].

Two types of phototherapy are used in the treatment of psoriasis. UVB phototherapy (so called TL01 excluding the most erythematogenic UVB) has acquired a position next to puvatherapy (associating co-administration of a psoralen either by oral intake or bath, with exposure to UVA) of which the efficacy has been clearly established for a long time. The use of UVB TL01 phototherapy presents less constraint but doesn't seem to be as efficient as puvatherapy in the more severe forms. The results of these two phototherapies are amplified by the addition of adjuvant treatments, in particular with the association of the oral intake of acitretin. The long-term risk of phototherapy is the induction of cutaneous cancers, essentially spinocellular carcinomas; this risk, qualified and quantified for puva, remains less clear for TL01; it imposes the need for a precise count of the number of sessions received and a prolonged follow-up of patients having received numerous phototherapy treatments. The indication for phototherapy is an extensive flare-up of psoriasis in its common form. Therapeutic rotation, during successions of flare-ups or when the phototherapy capital has been consumed, can be done with a retinoid or methotrexate, conversely it has to be much more careful with cyclosporin due to the increase of the carcinogenic risk.