This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Papulosquamous Disorders, Subject name: Skin
[{'content': 'Herald patch is seen in: \nSelect and explain. \nA. Pityriasis rosea, B. Lichen planus, C. Pityriasis alba, D. Taenia versicolour', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans: a (Pityriasis rosea) Ref: Harrison, 16th ed p. 292; 17th ed, p. 317, Roxburgh's Common skin d/s, 17th ed, p. 17Herald patch is seen in pityriasis roseaPITYRIASIS ROSEAIt is an acute exanthematous papulosquamous eruption often with a characteristic self limiting course.Etiology is unknown, but 2 agents are suggested which include HHV-7 and legionella micadedi.* Most commonly affects young adults (F>M)* Predominant involvement is limited to the trunkThe first feature is a single annular plaque usually on the trunk (herald patch)* Principal lesions are oval or circular with long axis of oval lesion following lines of cleavage in a Christmas tree pattern(fir tree pattern)Lesion may have fine scaling (cigar paper scales)", 'role': 'assistant'}]