Pityriasis Rubra Pilaris By Shinjita Das, MD, Harvard Medical School Reviewed / Revised Aug 2021 | Modified Sep 2022 View Patient Education Diagnosis Treatment Topic Resources Pityriasis Rubra Pilaris... Pityriasis Rubra Pilaris... Pityriasis Rubra Pilaris... Pityriasis rubra pilaris is a rare chronic disorder that causes hyperkeratotic yellowing of the skin, including the trunk, extremities, and, particularly, the palms and soles.