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What is Herald patch is seen in: and explain in detail?
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)