To the Editor I read with great interest the study by Lim et al1 on the use of afamelanotide in combination with narrowband UV-B for treating vitiligo. So far, there is no truly satisfactory treatment for vitiligo, so any new approach is most welcome. However, this study raises several issues. Afamelanotide binds with the melanocortin-1 receptor (MC1R), which is the receptor upstream of one of the key pathways for melanogenesis.2 Unfortunately, MC1R is not expressed by melanocyte stem cells, and thus afamelanotide can stimulate pigmentation and increase proliferation of melanocytes but cannot have any effect on the differentiation of melanocyte stem cells.3
Passeron T. Indications and Limitations of Afamelanotide for Treating Vitiligo. JAMA Dermatol. 2015;151(3):349–350. doi:10.1001/jamadermatol.2014.4848
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