Abstract: Melanonychia significantly affects aesthetics and patient well-being, particularly when it advances to subungual melanoma. The causes of melanonychia are multifactorial, encompassing nail matrix melanocyte activation, benign melanocytic proliferation, subungual melanoma, as well as inflammatory, infectious, traumatic, and drug-induced conditions. Among these, subungual melanoma poses a diagnostic challenge due to its nonspecific clinical presentation, leading to delayed or missed diagnoses that adversely affect prognosis. Accurate differentiation between malignant melanonychia and more common benign etiologies—such as onychomycosis, trauma-related pigmentation, drug-induced pigmentation, and subungual warts—is essential to avoid both misdiagnosis and overtreatment. This review summarizes the clinical, dermoscopic, and histopathological characteristics of melanonychia of various origins; highlights key dermoscopic features for distinguishing subungual melanoma from non-melanocytic pigmentation; and outlines diagnostic and therapeutic strategies tailored to both adults and children. Clarifying these distinctions is critical for facilitating earlier recognition of nail melanoma while minimizing unnecessary interventions for benign conditions. Keywords: melanonychia, nail malignant melanoma, diagnosis and treatment, dermoscope
Huang et al. (Sun,) studied this question.