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| Fig. 2.8 Koebner (isomorphic) phenomenon. Patient with acute
explosive psoriasis demonstrating restriction of lesions to the site of
minor trauma in the form of a sunburn. (Courtesy of the William L.
Weston, M.D. collection.) |
Traumatizing the epidermis of a patient with a certain preexisting skin disease will cause the same skin disease to form in the traumatized skin. Noticing this skin finding is helpful when creating a differential diagnosis. Only certain diseases are associated with a Koebner phenomenon; lichen planus, lichen nitidus, and psoriasis (Fig. 2-8) are examples.
