Segmental vitiligo following nine-valent human papillomavirus vaccination: A case report.

Human papillomavirus (HPV) vaccines have significantly reduced the burden of HPV-related malignancies, with the nine‑valent vaccine demonstrating an excellent safety profile. We report a rare case of segmental vitiligo in a 22‑year‑old woman following the standard three‑dose regimen. The patient developed erythema and itching on the right eyebrow after the second dose. Within a week after the third dose, a large hypopigmented spot appeared in the same area and rapidly extended to the ipsilateral forehead and bridge of the nose. Clinical examination, supplemented by dermoscopy, Wood's lamp evaluation, and reflectance confocal microscopy confirmed the diagnosis of segmental vitiligo. The patient was subsequently treated with a combination of the Janus kinase (JAK) inhibitor tofacitinib citrate, 308 nm excimer laser, fractional laser, and topical tacrolimus 0.1% ointment, achieving approximately 70% repigmentation at thirteen-month follow-up. Although the close temporal association raises the possibility of a vaccine-triggered immune response - potentially through mechanisms such as bystander activation, epitope spreading, or molecular mimicry - this report describes a correlation, not a proven causal relationship. Current evidence is insufficient to establish causality. This case underscores the need for ongoing post‑marketing surveillance and mechanistic studies to elucidate the interplay between vaccination and autoimmune phenomena, while reaffirming the overall favorable benefit - risk profile of HPV vaccination.