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Indian Journal of Dermatology, Venereology, Leprology, Vol. 70, No. 6, November-December, 2004, pp. 375 Letter To Editor Vitiligo and lichen planus in striae: Is it Koebner phenomenon? Lahiri Koushik, Malakar Subrata Consultant Dermatologist, Rita Skin Foundation, Kolkata Code Number: dv04129 Sir, We read with great interest the article, "The isomorphic phenomenon of Koebner" by Thappa DM.[1] It is indeed a good compilation. In this regard we would like to add a few words. Koebner phenomenon (KP) refers to the development of isomorphic lesions in the traumatized area of normal skin in certain skin diseases.[2] Recently Koebner phenomenon has further been subdivided into two classes: KP-h (KP from history) and KP-e (experimentally induced KP).[3] But in both the cases only external trauma can induce this phenomenon. We have documented the spread of vitiligo and lichen planus, two representative diseases in which KP occurs, along stretch marks.[4],[5] The pathology of striae essentially lies in the sub-epidermis, while the overlying epidermis remains normal, except for some thinning.[6] Whether stress rupture of the connective tissue framework is the real cause of striae is still a matter of controversy,[7],[8] but there is unanimity that other than thinning and flattening the epidermis remains intact and the clinical picture is the visible result of the dermal changes.[9] The dermal collagen is layered in thin eosinophilic bundles, oriented in straight lines parallel to the surface in the direction of presumed stress. Scanning electron microscopy reveals some amorphous sheet-like structures.[10],[11] These changes should not initiate the changes of LP, where the primary defect is epidermal basal cell damage. That these changes were not produced by scratching was indicated by the fact that the intervening normal skin was unaffected. Lesions of LP developed only along the course of stretch marks.[5] Similarly in vitiligo the pathological changes are in the basal cell layer of the epidermis. How a fundamentally sub-epidermal condition like striae can trigger the spread of vitiligo and/or lichen planus is still an unanswered question. REFERENCES
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