Light-induced skin lesions in lupus erythematosus: photobiological studies.

To investigate the light sensitivity to various wavelength regions in lupus erythematosus (LE), phototests were performed in 24 LE patients with clinical photosensitivity (7 had systemic LE, 9 discoid LE, and 8 subacute cutaneous LE). Skin areas (measuring 40-60 cm2) were irradiated daily, maximally six times. With all three light sources used (emitting UVB, UVA, and visible light respectively) abnormal papular or papulosquamous reactions could be induced. In four of the 20 patients reacting abnormally, lesions occurred 10 or more days after cessation of the phototests; this indicates that the problem of photosensitivity in LE may be greater than appreciated so far.