Zigzag longitudinal melanonychia: a peculiar dermoscopic pattern.

Abstract

Longitudinal melanonychia (LM) can present a diagnostic challenge and dermoscopy is of utmost importance for its evaluation and differential diagnosis of LM. This report aimed to describe an unusual dermoscopic pattern in a group of patients that presented with LM. The clinical course and features of five LM patients that presented with an unusual 'zigzag' dermoscopic pattern were analyzed retrospectively. In all, four of the five patients were children (age range: 10-13years). In all five patients, the thumb nail was affected. A nail matrix biopsy was available for only one patient and was reported as lentigo. In two (one child and one adult) out of the five patients, spontaneous total regression of the LM was observed. The peculiar 'zigzag' dermoscopic pattern of LM described herein seems to occur primarily in children. Although this pattern is a benign in nature, it is not clear if it is related to trauma. Further investigation is warranted to clarify the association between the histopathological findings and the zigzag pattern observed via dermoscopy.