THE HYPERPERFUSION OF THE PSORIATIC PLAQUE CORRELATES HISTOLOGICALLY WITH DILATATION OF VESSELS

We examined psoriatic lesions on the upper legs in 20 patients, using a two-dimensional Laser-Doppler-Scanner (Laser Doppler Perfusion Image r LDI, Lisca Development, Linkoping/Sweden). The plaques were evaluate d meekly during therapy with dithranol. Five plaques were reconstructe d three-dimensionally before and after therapy (reconstruction program ANAT 3D, SIS, Munster, Germany). The psoriatic plaque was represented in the Laser Doppler Perfusion image as a sharply demarcated, hyperpe rfused area. The perfusion of the plaques dropped during therapy with dithranol to just slightly increased values, compared with normal skin (2.01 arbitary units AU, healthy skin 1.1 AU). Using three-dimensiona l reconstruction, we investigated the volume of dermal vessels and the density of papillae. When compared, the volume of papillary vessels w as twice as large in psoriatic as in healthy skin. The number of the p apillae per square millimetre, detected by three-dimensional reconstru ction, was not reduced significantly during therapy. We think that the increased perfusion of the psoriatic plaque is due to the combination of morphological (dilatation of vessels), dynamic (increased blood fl ow) and optical effects (reduced scattering and increased sampling dep th of the laser-beam in acanthotic tissue).