Supplementary Material for: Focal hypertrichosis during topical tacrolimus therapy for vitiligo: A case report

Introduction: Tacrolimus is widely used in treating vitiligo. Drug-induced hypertrichosis is a well-known side effect of cyclosporine. It is less commonly associated with tacrolimus or with topical calcineurin inhibitors. Four reports of hypertrichosis attributed to topical or systemic tacrolimus have been previously reported in the literature. In this report, we describe a case of focal hypertrichosis due to long-term use of topical tacrolimus for vitiligo. Case Presentation: A 15-year-old boy with focal hypertrichosis of white hair for four months, after treatment with topical tacrolimus 0.1% ointment. He denied ever using other ointment to the area. After he stopped using tacrolimus for half a month, the focal hypertrichosis improved. Conclusion: We propose that the focal hypertrichosis was induced by tacrolimus. The hair growth stimulating effects of tacrolimus have been established. It is reported that tacrolimus directly stimulates mouse whiskers in vitro and prolongs the anagen phase of hair growth when it is applied topically in mice. We believe that a greater awareness of this rare side effect of tacrolimus is warranted, as tacrolimus is widely used in treating vitiligo.