Clinical significance of Koebner phenomenon in vitiligo

Background The clinical significance of Koebner phenomenon (KP) in vitiligo with respect to disease activity and course is still debatable. Recently, a new classification was introduced for the assessment of KP. Objectives To evaluate the new assessment method for KP in clinical practice and to determine its clinical significance, both with respect to the clinical profile, course of vitiligo and treatment response. Methods Seven hundred patients with generalized vitiligo were included in this observational cohort study. KP was classified according to the new classification system into different subtypes [KP1, by history; KP2A and KP2B, by clinical examination (A, lesions on friction areas; B, linear, artefactual lesions)]. Results KP1 was positive in 34 1% of the patients, 66 3% were KP2A positive and 15 1% showed KP2B. The body surface area (BSA) was significantly (P < 0.001) higher in the presence of any KP subtype and more disease activity was found in KP1-positive and KP2B-positive patients. An earlier age at onset and elevated risk of further depigmentation despite treatment were observed in all KP-positive groups. In KP2A-and KP2B-positive patients, depigmentation of wrists/ankles was more common. In the KP2A-positive group, a significantly higher prevalence of thyroid disease was found while autoimmune diseases were less prevalent in KP2B-positive patients. Conclusion The new assessment method for KP, taking into account both history and clinical examination, seems to be a useful and valuable tool for assessing KP in daily practice. Our results support the hypothesis that KP may function as a clinical parameter to assess and predict the clinical profile and course of vitiligo.