PSORIATIC PLAQUES EXHIBIT RED AUTOFLUORESCENCE THAT IS DUE TO PROTOPORPHYRIN IX

In evaluating the autofluorescence properties of normal and diseased s kin we discovered that psoriatic plaques can emit a distinct red fluor escence when illuminated with WA or blue light. Using a macrospectrofl uorometer equipped with a 442 nm excitation laser, a sharp in vivo flu orescence emission peak around 635 nm could be demonstrated within the plaques of 34 of 75 (45%) patients with psoriasis, This peak was abse nt from normal appearing skin of psoriatic patients and also from the skin of 66 patients with other dermatologic diseases. A microspectrofl uorometer coupled with the same excitation laser was used to obtain em ission spectra of separated epidermal sheets and dermis from plaques d emonstrating macroscopic red autofluorescence. An emission peak around 635 nm was observed in all three patients thus studied, but only on s pectra obtained from the epidermis. Additional spectra of vertical mic roscopic sections of intact psoriatic skin from five other patients re vealed that the peak originated from the stratum corneum, Emission spe ctra from other microlocations including the mid-epidermis and dermis of psoriatic and normal skin, as well as the stratum corneum of normal skin, failed to demonstrate a 635 nm peak. The excitation and emissio n fluorescence spectra of acid extracts of psoriatic scale from five p atients were all similar to those of protoporphyrin IX in acid solutio n. High performance liquid chromatography identified the presence of p rotoporphyrin IX in the acid extracts from psoriatic scale of the same patients. We conclude that native psoriatic plaques can exhibit red a utofluorescence that is due to elevated levels of protoporphyrin IX wi thin scales.