Koebner Phenomenon

[This phenomenon is also termed the isomorphic response]

Appearance of new skin lesions on previously unaffected skin secondary to trauma.
Koebner phenomenon seen in –

1. Psoriasis,
2. Vitiligo,
3. Lichen planus

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Koebnerization – function as a clinical indicator of disease activity in vitiligo, as well as serve as a predictor of treatment response

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Other conditions have demonstrated the Koebner phenomenon

1. leukocytoclastic vasculitis
2. mycosis fungoides
3. eruptive xanthomas

Classification and Subtypes of the Koebner Phenomenon

Boyd and Nelder classified

First group [category I] referred to as true koebnerization,

1. psoriasis,
2. lichen planus,
3. vitiligo.

Koebner phenomenon is reproducible in all patients by a variety of insults.

Boyd and Nelder argued that the term Koebner phenomenon should be typically reserved for this group of diseases.

Second group [category II] –pseudo-koebnerization,

1. molluscum contagiosum
2. verruca vulgaris

whereby the Koebner phenomenon gets produced by the seeding of infectious agents along with sites subjected to trauma, usually from scratching.

Third group [category IIII],  occasional lesions,

1. Darier disease
2. Erythema multiforme,

which meet some criteria for the Koebner phenomenon but not all.

Fourth group [category IV] – questionable trauma-induced process, includes all disorders with a dubious association with trauma, such as pemphigus vulgaris and lupus erythematosus.