A 16-year-old boy presented with asymptomatic, multiple, erythematous, annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. The most likely diagnosis is:
Lesions predominantly localized to the trunk and their erythematous nature with other features of pityriasis lead to diagnosis of pityriasis rosea. Ref: Anthony Du Vivier, Phillip H. McKee, Chapter 6, "Pityriasis Rosea and Pityriasis Rubra Pilaris", In the book, "Atlas of Clinical Dermatology", Elsivier Publication, 2002, 3rd Edition, Spain, Page 87
Pityriasis versicolor
Pityriasis alba
Pirityasis rosea
Pityriasis rubra pilaris