<prompt> A patient presents with erythematous scaly lesions on extensor aspect of elbows and knee. The clinical diagnosis is got byAuspitz signKOH smearTzanck smearSkin biopsy  <response>: Erythematous scaly lesions on extensor aspect of elbow and knee favours the diagnosis of Psoriasis.The clinical diagnosis of psoriasis can be made by demonstrating Auspitz sign.It is a characteristic finding of psoriasis in which removal of scale leads to pinpoint bleeding. 