Ectopic Acanthosis Nigricans at a Post-Syndactyly Surgical Site: An Unusual Reactive Epidermal Phenomenon

This article discusses a rare case of ectopic acanthosis nigricans (AN) occurring at a post-surgical site in a 20-year-old woman who had syndactyly-release surgery with medial thigh grafts in infancy. The patient presented with hyperpigmented and hypertrichotic plaques in the interdigital web spaces of her hands. Dermoscopy and histopathology confirmed the diagnosis of ectopic AN, characterized by hyperkeratosis, papillomatosis, and basal layer pigmentation. The study suggests that ectopic AN is a reactive epidermal phenomenon due to epidermal–dermal mismatch and altered growth factor signaling in grafted skin. Recognizing this rare condition is crucial to prevent unnecessary metabolic or malignancy evaluations.