[Lichenoid pityriasis. Clinical study of 13 cases].

13 patients with Pityriasis Lichenoides are studied clinical and histologically, showing a clinical polymorphism of the lesions, mainly in the papulous, vesiculous, and necrotic ones. The data about age, sex, evolution and response to the treatment in the present study are similar to those found by other authors. Constantly, we found, a variable degree of vasculitis. In almost all the cases there was a damage of the epithelium --exoserosis and exocytosis--, as well as presence in some cases, of red cells extravasated within the epidermis. In upper dermis we found in all biopsies, divers degrees of perivascular cell infiltration mainly composed of lymphocytes and histiocytes with predominance of the last ones, in five cases. In the majority of our cases, there was a strong relationship between the clinical and the histological aspects, but in some cases, mild lesions showed an acute microscopical picture. We are of the opinion that Pityriasis Lichenoides must be considered as a different entity from Parapsoriasis. In addition, we think that PL, is a clinical picture that manifests itself as a chronic or an acute form, and both types can be seen in the disease evolution. Finally, we could not find an evident influence and a positive response to the treatment in our patients with the classical therapeutics.