Melanotic macule of nail unit and its clinicopathologic spectrum ScienceDirect Longitudinal melanonychia and skin hyperpigmentation associated with hydroxychloroquine therapy JAAD Case Reports Differential diagnosis of pigmented nail lesions Anais Brasileiros de Dermatologia This dark line or discoloration on the nail can be a common condition called melanonychia, basically, extra pigment in the nail plate. In many people, especially those with more melanin in their Longitudinal Melanonychia MDedge An Evidence Based Approach to Pediatric Melanonychia Dermatologic Clinics