Phototherapy in the perspective of the chronicity of psoriasis.

According to the guidelines for the treatment of psoriasis, phototherapy is given in courses of UVB exposure starting at 50-70% of the minimal erythema dose, MED, with subsequently incremental dosages, but keeping erythemal skin reactions to a minimum by restraining the dosages when necessary. In this review, this classical principle of short-term near erythematogenic UVB therapy without further UVB maintenance therapy is challenged as it is evidently not optimal for psoriasis as a chronic condition. There is old experimental evidence supplemented with growing knowledge on the mode of action of phototherapy and more recent data on low-level UVB regimens as maintenance therapy that should urge us to revisit our guidelines on phototherapy to address psoriasis for what it is: a chronic condition.