Vitiligo-Like Depigmentation following Treatment with Imiquimod 5% Cream for Condylomata Acuminata

Imiquimod cream is an immunomodulatory agent that has been approved by the US Food and Drug Administration for use in the treatment of anogenital warts (condylomata acuminata) due to its local immune effects in activating Toll-like receptors 7 and 8 on antigen-presenting cells, resulting in reduction of the viral load of human papillomavirus with subsequent wart regression. After its application, some side effects are commonly reported, including erythema, edema, scaling, erosion, and ulceration. While pigmentary changes, including vitiligo-like depigmentation, have been mentioned as a possible side effect, they have rarely been reported in the literature. Alterations in pigmentation occur because imiquimod application causes human melanocyte apoptosis and autodestruction resulting in loss of melanocytes. Herein, we report the rare case of a 34-year-old healthy male who developed vitiligo-like depigmentation following imiquimod application for his genital warts. This case report aims to increase physicians’ awareness of this possible side effect that could be irreversible and difficult for the patient to accept.

Human melanocyte development and melanoma dedifferentiation at single cell resolution

SUMMARYIn humans, epidermal melanocytes are responsible for skin pigmentation, defense against ultraviolet radiation, and the deadliest common skin cancer, melanoma. While there is substantial overlap in melanocyte development pathways between different model organisms, species dependent differences are frequent and the conservation of these processes in human skin remains unresolved1–3. Thus, the biology of developing and adult human melanocytes remains largely uncharacterized. Here, we used a single-cell enrichment and RNA-sequencing pipeline to study human epidermal melanocytes derived directly from skin, capturing transcriptomes across different anatomic sites, developmental age, sexes, and multiple skin tones. Using donor-matched skin from distinct volar and non-volar anatomic locations, we uncovered subpopulations of melanocytes exhibiting site-specific enrichment that occurs during gestation and persists through adulthood. In addition, we identified human melanocyte differentiation transcriptional programs that are distinct from gene signatures generated from model systems. Finally, we use these programs to define patterns of dedifferentiation that are predictive of melanoma prognosis. Overall, the characterization of human melanocytes fresh from skin revealed new subpopulations, human-specific transcriptional programs, and valuable insights into melanoma dedifferentiation.