Instrumentation and action spectra in light-associated diseases.

Instrumentation for studying action spectra in controls and various light-associated diseases is described. This study summarizes tests performed with a prism grating monochromator during the last 10 yr. There were 68 photodermatoses studied: xeroderma pigmentosum (XP) (1), lupus erythematosus (LE) (12), polymorphous light eruption (PLE) (23), solar urticaria (4), actinic reticuloid (2), halogenated salicylanilide photosensitivity and persistent light reactors (11), psoralen photosensitivity (6), and porphyria (9). A normal minimal erythema dose in the UVB (below 320 nm) was generally observed in polymorphous light eruption and lupus erythematosus. The most exquisite photosensitivity for delayed erythema was observed in actinic reticuloid, which in one case was 25-35 times more sensitive in the UVB range which was also observed but to a lesser extent in XP and in persistent light reactors. Persistence of erythema and edema at test sites was observed in XP, PLE, LE, and actinic reticuloid. A delay in development of erythema reaching a maximum at 72 hr was observed in XP and psoralen phototoxicity. Maximum photosensitivity occurred in solar urticaria. Three patients had peak sensitivity in the range of 310-313 nm and the 4th at 460 nm. Photosensitivity in the visible range was detected in 2 patients with solar urticaria, one with actinic reticuloid, and confirmed in 9 patients with porphyria (405 nm). Photosensitivity in the UVA (above 320 nm) occurred to some degree in all groups.