Photosensitivity and cutaneous acid hydrolases in porphyria cutanea tarda.

In the present study the participation of lysosomal enzymes in the primary photosensitizing process in the skin of porphyric patients were investigated. Cutaneous photosensitivity reactions were produced in patients with porphyria cutanea tarda by irradiation with near UV light and also to a lesser degree with visible light. The reactions occurred almost exclusively in patients with urinary uroporphyrin excretion exceeding 900 nmol/24 h and preceeded any noticeable increase of lysosomal enzyme activity by several hours. These results indicate that lysosomal enzymes are not primarily involved in the photosensitizing reaction in porphyric patients but that they participate in the cutaneous inflammatory process in porphyric skin at a later stage.