Clinical and Dermoscopic Features of Fungal Melanonychia: Differentiating from Subungual Melanoma

BACKGROUND: Fungal melanonychia (FM) is a rare nail disorder that presents as dark pigmentation in the nail plate because of fungal nail infection. The diagnosis of FM is occasionally confusing because its appearance is similar to melanonychia due to other causes including malignant melanoma. Dermoscopy could help increase the accuracy of diagnosing the cause of pigmented nail lesions. However, dermoscopic features of FM are not well elucidated. OBJECTIVE: This study aimed to investigate clinical and dermoscopic characteristics of FM. METHODS: The clinical features and dermoscopic findings of 20 patients diagnosed with FM and 14 patients diagnosed with subungual melanoma the Department of Dermatology of Pusan National University Hospitals (Busan and Yangsan) were retrospectively reviewed. RESULTS: FM mainly occurred as a solitary form in the toenail. Patients in the FM group were older than those in the subungual melanoma group. The most distinguishable general dermoscopic features in FM were a distal diffuse pattern, distal linear pattern, and light brown to yellowish color. FM-associated specific dermoscopic patterns such as the reverse triangular pattern, subungual hyperkeratosis, scale on the nail surface, and white or yellowish streaks were dominantly observed in the FM group compared to the subungual melanoma group. CONCLUSION: FM-associated dermoscopic patterns and distal diffuse and linear patterns could be helpful diagnostic clues for differential diagnosis of FM from subungual melanoma.