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1178 SHORT COMMUNICATION Long-term Use of Topical Bimatoprost on Rhododendrol-induced Refractory Leukoderma: A Case Report Saki FUKAYA 1 , Masahiro KAMATA 1 *, Tomoko KASANUKI 2 , Makoto YOKOBORI 2 , Shintaro TAKEOKA 1 , Kotaro HAYASHI 1 , Takamitsu TANAKA 1 , Atsuko FUKUYASU 1 , Takeko ISHIKAWA 1 , Takamitsu OHNISHI 1 , Satoshi IIMURO 2 , Shinichi WATANABE 1 and Yayoi TADA 1 1 Department of Dermatology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605, and 2 Teikyo Academic Research Center, Teikyo University, Tokyo, Japan. *E-mail: [email protected] Rhododendrol (RD) inhibits melanin synthesis, and has been used in skin-whitening cosmetic products. How­ ever, some individuals have developed leukoderma on the skin at the site of RD application and refractory depigmentation has occurred even after ceasing appli- cation of RD (1–4). Skin-whitening cosmetic products containing RD were discontinued in 2013. Bimatoprost is a prostaglandin F2α analogue, which is often used to promote eyelash growth (5) for cosmetic reasons and in the treatment of glaucoma (6, 7). Following reports that bimatoprost induces skin pigmentation as an adverse effect (8–12), we previously conducted an open-label single-centre pilot study to evaluate the effectiveness of bimatoprost on refractory RD-induced leukoderma (13). Following the previous study, in which patients applied bimatoprost for 6 months, one patient requested to continue application of bimatoprost. Five months after Accepted Aug 22, 2019; E-published Aug 22, 2019 discontinuation of bimatoprost at the end of the pilot study, she re-started topical application of bimatoprost and continued for 14 months. We report here a case of refractory RD-induced leukoderma treated with bimato- prost for approximately 1.5 years in total. CASE REPORT A 40-year-old Japanese woman started using cosmetics containing RD in April 2011. She developed leukoderma on her face and neck in April 2013 where she had applied RD. Thereafter, she disconti- nued the cosmetics containing RD in August 2013. Although the leukoderma on her face gained repigmentation without any further treatment after discontinuation of RD, the leukoderma on her neck had not improved for more than 3 years. The patient was enrolled in the previous pilot study to evaluate the effectiveness of bimatoprost on refractory RD-induced leukoderma in November 2016 at the age of 45 years (patient number RD-07), and applied bimatoprost on leukoderma on the left side of the neck once daily for 3 months, and then twice daily for another 3 months. The method is described in detail in the previous paper (13). The area of leukoderma on her neck, which was treated with bimatoprost, redu- ced in size significantly (Fig. 1A, B), and the patient requested to continue applying bimatoprost after the end of the study. After receiving another approval from Teikyo University Institutional Review Board, 5 months after discontinuation of application of bimatoprost in the study, she re-started to apply bimatoprost on leukoderma on both the right and left side of her neck and continued application of bimatoprost for 14 months (Fig. 1C, D). The areas of leukoderma reduced in size further after application of bimatoprost. Fig. 1. Case report. (A) Rhododendrol (RD)- induced leukoderma before topical application of bimatoprost to the neck. (B) RD-induced leukoderma on the neck 6 months after starting application of bimatoprost in the pilot study. (C) RD-induced leukoderma 5 months after discontinuation of topical application of bimatoprost and before re-starting to apply bimatoprost. (D) RD-induced leukoderma 14 months after re-starting to apply bimatoprost. mo: month; mos: months. (E) Changes in the results of the colour-difference meter on leukoderma on the left side of the neck. Time 0: time at which bimatoprost application was started in the pilot study in this patient. Circle: L* value; triangle: a* value; square: b* value. doi: 10.2340/00015555-3299 Acta Derm Venereol 2019; 99: 1178–1179 This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica.