Abstract
Onychopapilloma is a rare benign neoplasm of the nail bed and the distal matrix. It is the most common cause of monodactylous localized longitudinal erythronychia. Splinter hemorrhage, onycholysis or distal splitting are usually accompanied due to the subungual keratotic growth located in the corresponding linear streak. A 50-year-old female was referred for the evaluation of 1-mm width of erythematous band on the left thumbnail. Distal onycholysis and splinter hemorrhages were seen along the streak with a thread-like horny papule beneath the edge of the nail plate. On histopathologic examination, papillomatosis and acanthosis were observed in the distal nail bed epithelium. The upper layers of the nail bed epithelium showed matrix metaplasia. The nail plate specimen revealed subungual hyperkeratosis with focal hemorrhage. The histopathological findings confirmed the clinical diagnosis of onychopapilloma. Herein, we report a rare case of onychopapilloma presenting as a longitudinal erythronychia.