Longitudinal melanonychia in childhood: a clinical and histopathological review of Korean patients.

Longitudinal melanonychia is not frequently observed in children, and few studies exist on longitudinal melanonychia in paediatric patients, especially in Asian populations. We aimed to evaluate the clinical and histological findings of longitudinal melanonychia in Korean paediatric patients. A retrospective review of paediatric patients (≤18 years old) with longitudinal melanonychia who underwent nail biopsy between January 2010 and October 2015 was performed. Of a total of 21 patients with longitudinal melanonychia, there were 10 cases of functional melanonychia, eight of lentigo, and three of nevus, as determined by microscopic examination. Mild nuclear atypia was found in four cases, as well as a low degree of pagetoid spread in one case. No patient was diagnosed with melanoma. During the follow-up period, no signs of malignancy were noticed and one patient with nail matrix nevus showed complete spontaneous regression of the pigmented band. Clinical and histological features, generally accepted as signs suggestive of melanoma in adults, were more readily observed in benign conditions in children.