Atypical pityriasis rosea.

Six cases of pityriasis rosea with atypical morphology and distribution of the eruption are reported. The eruption did not show a typical 'Christmas-tree' arrangement, confined to the trunk and proximal parts of the extremities. However, the histology of the eruption revealed dyskeratotic cells in the epidermis and extravasated erythrocytes in the dermis, which were recently reported as rather characteristic findings of this disease. Prodromal symptoms, course and response to therapy were compatible with pityriasis rosea. Histological examination is important and helpful for the diagnosis of atypical cases.