Evolutionary changes of immunohistological characteristics of secondary lesions in pityriasis rosea.

In 15 patients with pityriasis rosea, we studied the evolutionary changes of the immunohistological characteristics of the secondary lesions. Many CD1a+ cells were seen in the epidermis and dermis of early lesions. In the well-developed lesions, the number of CD1a+ cells greatly increased in the dermis. In the late lesions, CD1a+ cells in the dermis significantly decreased as compared with the well-developed lesions. Early lesions showed a moderate T-cell infiltrate. In the well-developed lesions, the dermal T-cell infiltrate was dense, and the CD4 CD8 ratio was 2.9. The late lesions had a moderate T-cell infiltrate, in which the CD4 CD8 ratio significantly decreased as compared with the well-developed lesions. Thus, the relative decrease in CD4+ helper inducer cells during lesion regression, concomitant with a decrease in number of CD1a+ Langerhans cells, is in accordance with a broader concept of increased suppressor mechanisms during healing.