Abstract
Melanonychia, or melanin-derived brown-to-black nail pigmentation, is a diagnostic challenge for clinicians. The most serious disease of the nail unit, melanoma, primarily presents with melanonychia. However, melanonychia most often occurs as a result of benign etiologies such as nail matrix melanocytic activation, nail matrix melanocytic hyperplasia, and nail invasion by melanin-producing pathogens. Regrettably, patients with nail apparatus melanoma are often initially misdiagnosed, and due to diagnostic delays of an average of 2 years, melanoma of the nail unit carries a poor prognosis. Having a thorough knowledge of the various causes of melanonychia and using a systematic approach when evaluating brown-to-black nail pigmentation may help prevent misdiagnosis and thereby improve prognosis.
Highlights
Two-thirds of cases of nail apparatus melanoma (NAM) are characterized by melanin-derived brown-toblack nail pigmentation, or melanonychia [1]
Melanonychia is an ambiguous clinical finding that most commonly occurs as a result of benign etiologies such as nail matrix melanocytic activation, nail matrix melanocytic hyperplasia, and nail invasion by melanin-producing pathogens
Nail apparatus nevi were significantly associated with a brown coloration of the background and the presence of regular lines, while nail apparatus lentigines, ethnic-type pigmentation, and drug-induced pigmentation were significantly associated with homogeneous longitudinal thin gray lines and gray coloration of the background [3, 43]
Summary
Two-thirds of cases of nail apparatus melanoma (NAM) are characterized by melanin-derived brown-toblack nail pigmentation, or melanonychia [1]. Melanonychia is an ambiguous clinical finding that most commonly occurs as a result of benign etiologies such as nail matrix melanocytic activation, nail matrix melanocytic hyperplasia, and nail invasion by melanin-producing pathogens. Other nail pathogens, exogenous substances, and subungual hemorrhage can cause non-melanic brown-to-black nail pigmentation [1,2,3]. Patients with NAM are often initially misdiagnosed [2]. Having a thorough knowledge of the various causes of brown-to-black nail pigmentation and using a systematic approach when evaluating clinical cases may help prevent misdiagnosis and save a life
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