Mechanisms of ultraviolet (UV) B and UVA phototherapy.

Type:Uv phototherapy Time:2017-10-11 10:37:20

Ultraviolet (UV) radiation has been used for decades with great success and at a constantly increasing rate in the

management of skin diseases, becoming an essential part of modern dermatologic therapy (Krutmann et al, 1999). For

phototherapy, irradiation devices emitting either predominantly middlewave UV (UVB, 290-315 nm) or longwave UV (UVA,

315-400 nm) radiation are employed. In former years, patients were treated with broad-band UVB, broad-band UVA, or

combination regimens. Broad-band UV phototherapy, however, is being replaced more frequently by the use of irradiation

devices that allow treatment of patients' skin with selected emission spectra. Two such modalities which have their

origin in European Photodermatology are 311 nm UVB phototherapy (which uses long-wave UVB radiation above 300 nm

rather than broadband UVB) and high-dose UVA1 therapy (which selective employs long-wave UVA radiation above 340 nm).

In Europe, 311 nm UVB phototherapy has almost replaced classical broad-band UVB phototherapy and has significantly

improved therapeutic efficacy and safety of UVB phototherapy (van Welden et al, 1988; Krutmann et al, 1999). The

constantly increasing use of UVA-1 phototherapy has not only improved UVA phototherapy for established indications

such as atopic dermatitis (Krutmann et al, 1992a, 1998; Krutmann, 1996), but has also provided dermatologists with the

opportunity to successfully treat previously untractable skin diseases, e.g., connective tissue diseases (Stege et al,

1997; Krutmann, 1997). These clinical developments have stimulated studies about the mechanisms by which UVB and UVA

phototherapy work. The knowledge obtained from this work is an indispensable prerequisite to make treatment decisions

on a rationale rather than an empirical basis. Modern dermatologic phototherapy has started to profit from this

knowledge, and it is very likely that this development will continue and provide dermatologists with improved

phototherapeutic modalities and regimens for established and new indications. This review aims to provide an overview

about current concepts of the mode of action of dermatologic phototherapy. Special emphasis will be given on studies

that have identified previously unrecognized immunosuppressive/anti-inflammatory princ

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