[Dark nail: clinical findings, diagnostics and therapy of melanonychia].

BACKGROUND: A dark colored pigmentation of nails can be due to a subungual malignant melanoma. There are, however, many other benign causes and this differentiation is an important challenge in dermatological practice. PROBLEM: When should nail pigmentation be clarified by histological investigations?
MATERIAL AND METHODS: This article gives a survey of the literature on this topic and a review of own experiences with clinical case examples. The various causes of melanonychia are presented and criteria for the early recognition of melanoma of the nail matrix are formulated.
RESULTS: The width and depth of color of longitudinal melanonychia do not allow any conclusions on the dignity. If the nail striation is proximally broader than distally, this is evidence of a proliferative event. Confirmation of a subungual hemorrhage does not exclude a malignancy per se. Also detection of pigmentation due to fungi does not exclude the additional presence of a subungual melanoma. A systematic clinical analysis using clear criteria leads to a working diagnosis and suitable treatment.
CONCLUSION: An early and correct designation of nail pigmentation can avoid unnecessary nail interventions but can also be life saving.