ISSN: ISSN: 2157-7412
Yamamoto T and Ueki H
Koebner phenomenon indicates the newly appearance of isomorphic lesions at the sites of mechanically stimulated or injured skin. This phenomenon can be seen in various inflammatory, auto-immune, viral, fibrotic, and even tumoral disorders. Also, rheumatic diseases such as lupus erythematosus, dermatomyositis, and rheumatoid arthritis (RA) often present with cutaneous manifestations with isomorphic response of Koebner. RA presents with various skin conditions as extra-articular manifestations. Rheumatoid nodule is the representative specific skin lesion which frequently occurs on the hand, elbow, sole, sacrum, occipital area, and so on. These sites are susceptible to both outer and inner mechanical stress. Rheumatoid nodules involve not only skin but internal tissues such as spine, lung, heart valves, and gastrointestinal tract, which are also susceptible to mechanical stress. This isomorphic response may be induced at deeper levels than skin, and thus considered to be “deep” or “internal” Koebner phenomenon. Other than rheumatoid nodules, several specific skin conditions are associated with RA, such as palisaded neutrophilic granulomatous dermatitis and rheumatoid neutrophilic dermatitis, which can be seen on the fingers, elbows, knees and sole. Also, there are various other skin lesions in association with RA, which show Koebner phenomenon, such as neutrophilic dermatosis and autoimmune bullous diseases. Koebner phenomenon may be closely associated with the induction of various specific or nonspecific conditions, not restricted to the skin, in association with RA.