RESUMO
OBJECTIVE: Longitudinal melanonychia (LM) is a common dermatologic problem encountered in everyday practice. Its diagnostic approach is critical as it can be an early sign of nail melanoma. Racial melanonychia is the entity most frequently associated with LM. Because there are no clinical data regarding these associations in a Mexican population, we conducted a prospective study. METHODS: A total of 68 consecutive patients given the clinical diagnosis of LM were included and a nail biopsy was performed to determine its cause. RESULTS: Racial melanonychia was found in 48 cases (68%), 4 cases (5.7%) were associated with benign melanocytic hyperplasia, and 4 cases (5.7%) had a nail apparatus malignancy. LIMITATIONS: Dermatoscopy and immunohistochemical stains were not used. Incisional transverse nail matrix biopsies were performed when melanonychia affected the middle portion of the nail plate. CONCLUSION: LM is most commonly associated with racial melanonychia in the Mexican population, but in nearly 6% of cases it may be linked with nail apparatus malignancy. To our knowledge, this is the first time a study of this nature was performed in a mestizo Hispanic population.