RT Book, Section A1 Hardin, J. Matthew A2 Knoop, Kevin J. A2 Stack, Lawrence B. A2 Storrow, Alan B. A2 Thurman, R. Jason SR Print(0) ID 1181044164 T1 Pityriasis Rosea T2 The Atlas of Emergency Medicine, 5e YR 2021 FD 2021 PB McGraw-Hill PP New York, NY SN 9781260134940 LK accessmedicine.mhmedical.com/content.aspx?aid=1181044164 RD 2024/03/29 AB The 1st sign of pityriasis rosea (PR) is usually a well-demarcated, salmon-colored macule that evolves into a larger patch (1-4 cm) with peripheral scaling (“herald patch”). Over 1 to 2 weeks, generalized, bilateral, and symmetric macules and plaques appear along skin cleavage lines (termed “Christmas tree” pattern). The macules have a peripheral collarette of fine scaling. Most will have severe itching associated with the generalized eruption. The lesions slowly resolve over 6 to 8 weeks. Atypical presentations in children include inverse PR (presentation on the face, axillae, and/or inguinal areas) and papular PR (peripheral scaling papules with central, hyperpigmented plaques). A viral etiology is postulated due to seasonal variation and case clustering.