<prompt> Koebners phenomenon is not seen in:VitiligoPsoriasisDermatitis herpertiformisLichen planus  <response>: Ref: Thappa DM. The isomorphic phenomenon of Koebner. Indian J Dermatol Venereal Leprol 2004;70:187-9.Explanation:The Koebner phenomenon is the development of isomorphic pathologic lesions in the traumatized uninvolved skin of patients who have cutaneous diseases.Koebner phenomenon signifies activity of the disease.Types of Koebner phenomenon:1. True isomorphic phenomenon:There appear to be three disease processes that display the true isomorphic response of Koebner:PsoriasisLichen planusVitiligo.2. Pseudoisomorphic phenomenon:The Koebner phenomenon also seen in infectious diseasesWartsMolluscum contagiosumBehcets diseasePyoderma gangrenosum.3. Occasionally occurring isomorphic phenomenon:In this category, diseases occasionally localize to sites of trauma, e.g.Cancer gastric, testicular or mammary Dariers diseaseErythema multiformeHailey-Hailey diseaseKaposis sarcomaKyrles diseaseLichen sclerosus et atrophieusPellagraPerforating folliculitisReactive perforating collagenosis.Koebner response in psoriasis:The reported incidence of Koebner response in psoriasis varies from 11-75.The latent period between injury to uninvolved skin and appearance of disease is usually 10-14 days, but it may range from 3 days to several years.The reverse Koebner response:The reverse Koebner reaction is seen when an area of psoriasis clears following injury. 