Pityriasis Rosea (PR): Common acute papulosquamous eruption normally lasting 4-10 weeks. Most often begins as a single 2- to 4-cm thin oval plaque with a fine collarette of scale located inside the periphery of the plaque ("herald patch"). Similar-appearing, but smaller, lesions appear several days to weeks later, typically distributed along the lines of cleavage on the trunk ("Christmas tree" pattern). Usually asymptomatic, sometimes pruritic with mild flu-like symptoms. Occurs most commonly in teenagers and young adults. Probably a viral exanthem associated with reactivation of human herpes virus (HHV)-7 and sometimes HHV-6. Treatment is usually suppoive, although midpotency topical coicosteroids can reduce pruritus; high-dose acyclovir for 1 week may hasten recovery. Ref: Blauvelt A. (2012). Chapter 42. Pityriasis Rosea. In L.A. Goldsmith, S.I. Katz, B.A. Gilchrest, A.S. Paller, D.J. Leffell, N.A. Dallas (Eds), Fitzpatrick's Dermatology in General Medicine, 8e.