RT Book, Section A1 Clark, Matthew A1 Gudjonsson, Johann E. A2 Kang, Sewon A2 Amagai, Masayuki A2 Bruckner, Anna L. A2 Enk, Alexander H. A2 Margolis, David J. A2 McMichael, Amy J. A2 Orringer, Jeffrey S. SR Print(0) ID 1161328461 T1 Pityriasis Rosea T2 Fitzpatrick's Dermatology, 9e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9780071837798 LK accessmedicine.mhmedical.com/content.aspx?aid=1161328461 RD 2024/10/15 AB AT-A-GLANCECommon self-limited papulosquamous eruption typically lasting 5 to 8 weeks.Occurs worldwide in all races and age groups, with peak incidence between the ages of 10 and 35 years.Classically begins as an isolated 3- to 5-cm oval plaque on the trunk with a collarette of fine scale just inside the periphery, which plaque is called a herald patch.This is followed by a secondary eruption of similar appearing but smaller lesions on the trunk and proximal extremities, usually with their long axis along the lines of cleavage.Many atypical variants exist in contrast to the pattern described above.Pityriasis rosea can have associated systemic symptoms and pruritus, but many cases are asymptomatic.Etiology is unknown, but it is thought to be a viral exanthem most likely related to infection or reactivation of human herpesvirus (HHV)-6 and/or HHV-7.Usually only supportive treatment and reassurance is needed, but for severe cases acyclovir may hasten recovery and lessen symptoms.