The Koehner pnenomenon in sarcoidosis
The isomorphic response of Koebner can be observed not only in psoriasis, but also in several diseases including lichen planus, vitiligo vulgaris, and further in systemic diseases; such as in SLE (systemic lupus erythematosus) or sarcoidosis. Some important clinical findings in sarcoidosis are presented and discussed in this paper with special references to Koebner phenomenon. Several intriguining examples; such as mutual-, microscopical-, internal-, or intra-lesional- Koebner phenomena are introduced and presented with related cases and figures. As the pathophysiology of Koebner phenomenon, it could be speculated that the 1st step of non-specific inflammations locally induced by some environmental stimuli to the normal-appearing skin including trauma, heat, cold, sun exposure, metal, tattoo, dermatitis, infections, etc might be followed by the 2nd step of the disease-specific reactions based upon genetic, immunologic or inflammatory backgrounds after latent periods. The understanding and investigation of these Koebner phenomena are important to clarify the natures of sarcoidosis of unknown etiology.