A case of pityriasis rubra pilaris with associated focal acantholytic dyskeratosis complicated by Kaposi's varicelliform eruption.

The clinical and histopathological diagnosis of pityriasis rubra pilaris (PRP) can be difficult because clinical findings are often subtle in early stages, and microscopic findings can overlap with those of other skin diseases. Focal acantholytic dyskeratosis (FAD) can rarely be seen in PRP and can mimic Darier's disease, Grover's disease or other disorders characterized by these histopathologic features. Kaposi's varicelliform eruption is a widespread infection due to herpes simplex virus (HSV) types 1 and 2, coxsackievirus A16 or vaccinia virus, occurring in a preexisting dermatosis; only one case has been reported in PRP. We report a patient with PRP whose biopsies showed both herpes simplex infection and FAD. A complete understanding of the mechanism behind this eruption evolved gradually, aided in great measure by the histopathologic findings.