Vitiligo Potential Repigmentation Index: a simple clinical score that might predict the ability of vitiligo lesions to repigment under therapy

Funding sources: none. Conflicts of interest: none declared. Madam, Nonsegmental vitiligo (NSV) is the most common form of vitiligo.1 Although its exact pathogenesis is still to be fully understood, the depigmentation process is due to a progressive and chronic disappearance of epidermal and/or follicular melanocytes.2–5 Repigmentation of vitiligo lesions depends on the existence of available melanocytes from reservoirs located in the epidermis and the hair follicles.3–6 To date, there is no global method to evaluate the potential of repigmentation in NSV. We conducted a prospective observational study aiming to develop and validate a simple Potential Repigmentation Index (PRI), which could be useful in the daily management of patients with NSV. The study was approved by the local ethics committee of the Bordeaux University hospital. Patients aged over 18 years, for whom narrowband ultraviolet (Nb‐UVB) treatment was prescribed, and who had given their consent for participation, were examined under natural light and Wood’s lamp, before and after 6 months of phototherapy. The total number of lesions exceeding 10 cm2 was assessed for each patient, and each lesion was classified according to the system proposed in Figure 1, which comprises four types of lesion, A, B, C and D. Furthermore, the PRI was calculated for every patient by establishing the ratio between the number of lesions with an expected good response rate (type A + type B) and the number of usually refractory lesions (type C + type D). Thus, PRI = (type A + type B)/(type C + type D). Nb‐UVB therapy was performed twice weekly for 6 months. We started with 0·2 J cm−2, independent of the skin type, and increased the dose by 20% every session until we reached the minimal erythema dose, which caused mild erythema that disappeared the next day of the session. At each follow‐up visit, every lesion was photographed and the rate of repigmentation was evaluated under natural light and Wood’s lamp examination. The response to therapy for every single lesion was classified as positive (≥ 75% repigmentation) or negative (< 75% repigmentation). The global response for each individual was classified as good (≥ 70% of lesions with over 75% repigmentation), mild (50–70% of lesions with over 75% repigmentation) or poor (< 50% of lesions with over 75% repigmentation). Two‐paired Student tests were used to compare PRI in patients with poor, mild and good repigmentation. In addition we tested the link between PRI and the percentage repigmentation in general using a Pearson correlation test. Statistical analyses were performed using SAS software version 9.1.3 (SAS Institute Inc., Cary, NC, U.S.A.).