Abstract: 【Abstract】 Objective To investigate dermoscopic manifestations and features of melanonychia. Methods A retrospective analysis was carried out on dermoscopic images of 4 common types of melanonychia collected in Department of Dermatology, Xijing Hospital, the Fourth Military Medical University from January 2016 to July 2020. Results A total of 266 cases of melanonychia were collected, including 64 （24.1%） of subungual melanoma, 52（19.5%）of nail matrix nevi, 89 （33.5%） of subungual hemorrhage, and 61 （22.9%） of onychomycosis. Subungual melanoma and nail matrix nevi mostly occurred in the fingernails. To be specific, subungual melanoma most frequently occurred in the thumbnails （62.8%）, while nail matrix nevi mostly involved the 2nd - 5th fingernails （73.9%）. Subungual hemorrhage and onychomycosis mostly occurred in the toenails, and there were 51 （57.3%） cases of subungual hemorrhage of the toenails and 46 （75.4%） cases of onychomycosis of the toenails. Subungual melanoma mostly occurred in patients aged over 40 years （49 cases, 76.8%）, while the other 3 types of melanonychia mostly affected patients aged under 40 years. Dermoscopic manifestations of subungual melanoma mainly included regular longitudinal bands （35 cases, 54.7%） or irregular bands （25 cases, 39.0%） whose width was greater than 3 mm in 87.5% cases, Hutchinson sign （36 cases, 56.3%）, and ruptures （15 cases, 23.4%） which mainly were black-brown in color; dermoscopic manifestations of nail matrix nevi mainly were a single regular pigmented band （52 cases, 100%） whose width was less than 3 mm in 36 （69.2%） cases, and Hutchinson sign （26 cases, 50%）, while no ruptures were observed in nail matrix nevus lesions; subungual hemorrhage dermoscopically manifested as diffuse macules （74 cases, 83.1%）, and globular dark red or black hemorrhagic structures were observed in 85 （95.5%） cases; fungal melanonychia was dermoscopically characterized by irregular dark brown longitudinal bands （54 cases, 88.5%）. Conclusions Subungual melanoma was dermoscopically characterized by regular longitudinal bands with a width of greater than 3 mm, nail matrix nevi by regular longitudinal bands, subungual hemorrhage by diffuse macules, and onychomycosis by irregular longitudinal bands. Dermatoscopy can be used to identify melanonychia lesions and provide a basis for auxiliary diagnosis of subungual melanoma.

Key words: Nail diseases, Nevi and melanomas, Onychomycosis, Dermoscopy, Subungual hematoma, Longitudinal melanonychia