Dermoscopic patterns of fungal melanonychia: A comparative study with other causes of melanonychia

Background: Diagnosing fungal melanonychia (FM) is often difficult because it mimics melanonychia caused by other factors. Dermoscopy is helpful in the setting of nail pigmentation. However, the diagnostic characteristics of FM on dermoscopy are not fully elucidated. Objective: We sought to determine the dermoscopic characteristics of FM. Methods: We evaluated the dermoscopic patterns of FM diagnosed at 2 university hospitals from January 2010 to February 2016. We included nail matrix melanocytic activation, nail matrix nevi, and nail unit malignant melanomas as control groups for comparison. Results: In all, 18 FM, 24 melanocytic activation of the nail matrix, 27 nail matrix nevi, and 11 malignant melanoma cases were analyzed. Statistical analysis revealed that yellow color, multicolor pattern, nonlongitudinal homogenous pattern, reverse triangular pattern, subungual keratosis, white or yellow streaks, and scales on the nail were more frequent in FM. However, gray color, longitudinal pattern, and pseudo-Hutchinson sign were less frequent in FM than in controls. Limitations: This was a retrospective study from 2 university hospitals, with a small sample size. Conclusion: The results revealed distinctive dermoscopic patterns for FM. Therefore, dermoscopy can be a useful ancillary tool for diagnosing FM.