The Koebner phenomenon is one of the most well-known entities in dermatology. It 
was first described by Heinrich Koebner in 1876 as the formation of psoriatic 
lesions in uninvolved skin of psoriatic patients after cutaneous trauma. This 
isomorphic phenomenon is now known to involve numerous diseases, among them 
vitiligo, lichen planus, and Darier disease. The pathogenesis of the Koebner 
phenomenon is still obscure but may involve cytokines, stress proteins, adhesion 
molecules, and autoantigens. This contribution reviews the clinical 
manifestations of Koebner phenomenon, its provocative factors, suggested 
pathogenesis mechanisms, and the various skin conditions that exhibit this 
unique response.