Adult onset pityriasis rubra pilaris.

Pityriasis rubra pilaris (PRP) has always been an intriguing topic ever since its inception. It is a group of chronic disorders characterized by reddish orange plaques with pityriasiform scaling showing follicular keratoses, palmoplantar keratoderma, and sometimes, erythroderma. It occurs all over the world but with racial variations. Its incidence might vary and the age at onset, behavior, clinical appearance, and prognosis are considered to be very important for its classification. It may manifest either as Type I classical adult onset PRP, Type II atypical adult (onset) PRP, or Type VI PRP (HIV-associated PRP pityriasis rubra pilaris) in contrast to classical juvenile (Type III) and circumscribed juvenile (Type IV) encountered among children. Its diagnosis is largely clinical with microscopic pathology being a useful supplement, but it continues to be a therapeutic dilemma. We review the epidemiology of adult onset PRP here and take stock of the prevalent treatment options.