Koebner Phenomenon

Excerpt

The Koebner phenomenon (KP), first described in 1876 by Heinrich Koebner, is the appearance of new skin lesions on previously unaffected skin secondary to trauma. This phenomenon is also termed the isomorphic (from Greek, “equal shape”) response, given that the new lesions appear clinically and histologically identical to the patient’s underlying cutaneous disease. In other words, a patient with psoriasis who exhibits koebnerization (and is said to be “Koebner-positive”) develops new psoriasiform lesions along sites of skin injury, even if trivial. Koebner phenomenon can develop in any anatomic site, including in classic areas of psoriatic involvement and in regions that are usually spared, such as the face. The phenomenon shows dynamic behavior. Patients may be “Koebner-negative” at 1 point in life but may later become “Koebner-positive.”