Childhood longitudinal melanonychia: case series from Poland

INTRODUCTION: Longitudinal melanonychia (LM) is characterized by a tan, brown or black longitudinal streak within nail plate caused by the presence of melanin. LM is relatively common in dark-skinned population, infrequent in Caucasian population, and rare in children. AIM: We report epidemiological, clinicopathological and dermoscopic analysis of 8 cases of childhood LM from Poland, which is the largest series in the Central and Eastern European population. MATERIAL AND METHODS: Three hundred and forty-eight patients presenting with various nail pigmentation (in 2010–2016) were analysed. 72 cases of LM have been identified, including 8 cases of childhood LM (< 16 years of age), which were included in further analysis. RESULTS: Seven patients were boys and one girl, with mean age of 9 years (range: 6–13). More than a half (n = 5) presented skin phototype II. The most common location of melanonychia was the first left fingernail. Dermoscopy revealed heterogeneity of longitudinal lines colour in 5 cases. The irregularity of longitudinal line thickness in 5 cases and irregularity of parallelism in 5 cases was observed. Histopathological evaluation was performed in 4 patients, in 3 cases it revealed the presence of nail matrix nevus, in one case the presence of melanocytic proliferation of the lentiginous pattern along the dermoepidermal junction. CONCLUSIONS: Despite the fact that melanoma was not recognised in any case, such a possibility should always be considered as the cause of LM, even in the paediatric population. Dermoscopy seems to be useful in patient follow-up and management.