Pityriasis rosea: A histopathologic study.

The histopathologic features of pityriasis rosea (PR) have been considered by many authors to be compatible with those of dermatitis, but it is not surprising that histological difference may exist between PR and dermatitis. fifty patients of pityriasis rosea were included in this study. We studied the 50 biopsies including 9 biopsies from herald patches. The characteristic features were; absence or decrease of the granular cell layer, extravasation of red blood cells in papillary dermis and partly into the epidermis, dyskeratosis, liquefaction of basal cells, homogenization of papillary collagen, intraepidermal vesicles in apparently dry skin. In addition of these features, we observed prominent delling of epidermis and a typical spongiotic pattern not reported earlier. The biopsies from herald patches showed minor differences from the secondary lesions. We also compared the histopathological features of recent lesions with older lesions.