<prompt> A male is presenting with a violaceous papule which is pruritic. There is pterygium of nail with cicatracial alopecia. Diagnosis is-PsoriasisPityriasis rosealichen planusSeborrheic dermatitis  <response>: LICHEN PLANUS:- Inflammatory T cell mediated auto immune disorder affecting skin, hair,nails and mucous membranes. Four Ps- purple , polygonal and pruritic papule. Classic lesion- small polygonal shaped, and red violet, flat topped papule. Surface is slightly shiny transparent,and a network of fine,white lines called Wickhams striae or small grey white puncta is also seen. violaceous pruritic papules, pterygium and cictricial alopecia are charecteristics of lichen planus IADVL textbook of dermatology, page 1070 