<prompt> A 50 years old patient presented to the skin OPD with erythematous scaly plaques over trunk and extremities for last l0 years. Lesions are occasionally itchy. There is history of remission and relapse with exacerbation during winters. Most likely diagnosis is?Lichen planusPsoriasis vulgarisPityriasis roseaSeborrhic dermatitis  <response>: Ans: B. Psoriasis vulgarisRef: Neena Khanna 4he p. 40-48; Roxburg lVhe p. 128-42; Venkataram 1e p. 491Psoriasis psoriasis vulgaris:Psoriasis is chronic dermatosis characterized by unpredictable course of remission and relapse and presence of well defined silvery white scaly papules and plaques on erythematous base.Aggravated in winter.Lesions are mildly pruritic or non-pruritic. 