Longitudinal melanonychia in children: A clinical and histopathologic study of 40 cases

Objective: Very little has been published on longitudinal melanonychia in c hildren. Our objective was to determine the nature of melanocytic lesions i n pediatric patients with longitudinal or total melanonychia and to look fo r correlations between clinical and histologic features. Methods: All patients younger than 16 years of age with longitudinal or tot al melanonychia who were evaluated at our nail disorder outpatient clinic b etween September 1993 and September 1996 were included. The clinical and hi stologic features of the nail condition were determined in each case. Results: Forty patients were included. The final diagnosis was news in 19 c ases (junctional in 17 cases and compound in 2), lentigo in 12 cases, and f unctional longitudinal melanonychia in 9. The latter corresponded to a hype rpigmentation caused by melanocytic activation with no increase in the numb er of melanocytes. None of the patients had melanoma. Appearance within the first year of life, periungual pigmentation, and total melanonychia were c onsistent features in patients with melanocytic hyperplasia (lentigo or new s). Early onset of a dark broad lesion in a white patient was typical of me lanocytic hyperplasia, although none of these features were pathognomonic. Conclusion: Benign melanocytic hyperplasia (lentigo or nevus) was the cause of 77.5% of cases of longitudinal melanonychia in our overall pediatric po pulation and of 85% of cases in the subset of white patients. All the remai ning cases of longitudinal melanonychia were the result of melanocytic acti vation.