The effect of 13-cis retinoic acid on epidermal lysosomal hydrolase activity in Darier's disease and pityriasis rubra pilaris.

Five patients with Darier's disease and 6 patients with pityriasis rubra pilaris were treated with 13-cis-retinoic acid. Extracts of separated epidermis were assayed for extractable protein, lactic dehydrogenase, Cathepsin D, beta glucuronidase and neutral proteinase before beginning therapy and 2, 4 and 8 weeks after therapy had begun. The epidermal extracts from patients with pityriasis rubra pilaris before beginning therapy were similar to extracts from normal control patients. During the course of therapy with 13-cis-retinoic acid, protein extractability, lactic dehydrogenase and neutral proteinase did not change; there was a highly significant decrease in the specific activity of the lysosomal hydrolases Cathepsin D and beta glucuronidase. A similar but less dramatic fall was noted in the Darier's patients taking 13-cis-retinoic acid. Darier's patients also had a decrease in neutral proteinase activity before beginning therapy; the specific activity of this enzyme increased during the course of therapy. 13-cis-retinoic acid does not induce clinical remission by increasing the intracellular concentration of lysosomal enzymes in epidermis in vivo.