Longitudinal melanonychia presents, regresses differently in children from adults

Pediatric longitudinal melanonychia should be treated differently from longitudinal melanonychia in adults, as lesions may grow darker or wider before stabilizing or improving, according to a study.

Longitudinal melanonychia (LM) may be an early sign of nail melanoma in adults. However, benign LM in children often shows typical features of nail melanoma, including irregular broad bands and varying color that grows darker or wider over time, making it difficult to differentiate between the two.

“Nevertheless, the persistence of LM can lead to patient and parental anxiety, and a lack of large studies on the natural course of pediatric LM makes it difficult to alleviate these worries,” Si-Hyung Lee, MD, PhD, of the Seoul National University Hospital in Korea, and colleagues wrote.

To investigate the clinical features and natural course of pediatric LM and to identify factors associated with the prognosis of pediatric LM, Lee and colleagues conducted a retrospective, single-center study that included a total of 703 lesions in 381 children.

Among the patients included, most had a single lesion, more than half had nail-biting habits and fingernails were involved twice as often as toenails (68.5% vs. 37.5%). In contrast, congenital LM was rare (1.8%).

The researchers followed the patients for a median of 1.7 years from first visit (range, 0-19.6 years) and found that most cases showed no change (51.9%).

Approximately 15% of LM cases showed darkening at least once and the median duration of darkening was 3.8 years. Among those cases, 53.1% stopped getting darker and began to stabilize with a median time to stabilization of 2.7 years.

Most cases showed no change in width (74.5%), although 16% cases grew wider at least once and the median duration of widening was 6 years. Among the cases with observable widening, 23.9% stopped getting wider and started to stabilize with a median time to stabilization of 4.4 years.

The researchers found that approximately 3%, 5% and 10% of LM lesions were likely to completely regress within 3, 4.5 and 9.5 years after onset, respectively. Among patients with only one lesion, LM reached complete regression earlier.

Multivariate analysis showed that single lesions, lesions on the left hand or foot and homogenous color correlated with regression. Color becoming lighter was also positively correlated with complete regression.

Lee and colleagues noted that a very small portion of LM lesions (5.5%) reached complete regression.

They also highlighted the likelihood that because more than half of the patients had nail-biting habits, it is possible that right-handed LM is less likely to regress because the right hand is more likely to be the dominant hand and thus more likely to be exposed to trauma.