<prompt> Most common cause of erythema multiforme?Herpes simplexMycoplasmaVaricella zosterInfluenza virus  <response>: Ans. a Herpes simplex. Ref. Harrisons, Principles of Internal Medicine, 16the d., pg 112ERYTHEMA MULTIFORME A vesiculobullous disease. Pink red macules papules with dusky violet colour or petechiae center which later becomes vesicles is clue to diagnosis centrifugal spread. Targetiris lesions--characteristic. Preferred sites--distal extremities, mucous membrane. Hemorrhagic crusts of lips characteristic dd - herpes simplex, pemphigus vulgaris, paraneoplastic pemphigoid Lesions resolve in 3-6 weeks 