Nail Unit Blue Nevi: A 11-Case Series and Review of the Literature

Background Blue nevus of the nail apparatus is a rare entity and only isolated cases are reported in the literature. Objective The aim of this study was to better characterize blue nevus at the nail unit. Methods Retrospective analysis of all nail unit blue nevi from the Nail Group of the French Society of Dermatology was compared to the literature. Results Eleven cases were retrieved from 2002 to 2019 with an average age of 45 years. The majority were women (9/11) and acquired (10/11). Hands were more frequently involved (9/11) with a predilection for the thumb and 2 cases were located on the hallux. Nail unit blue nevus mostly presented as a well-delimited blue spot of the lunula (9/11) and histologically was of the common type (10/11). There was no malignancy. Conclusion Nail unit blue nevus is a rare asymptomatic benign entity, mostly acquired on the thumb or the hallux of women. The most frequent presentation is a painless blue spot on the lunula. Congenital blue nevi seem to only affect the paronychium. Main differential diagnosis is melanoma and histopathological examination is mandatory.