P476: How can we minimize nail dystrophic change in longitudinal melanonychia evaluation?

A surgical intervention is needed in longitudinal melanonychia patients when it is difficult to rule out malignancy. Injuries to the nail matrix are induced during nail surgery when the nail plate is excised from its primary attachments. Thus, nail dystrophy after nail surgery is inevitable. Therefore, a surgical technique to minimize nail dystrophy is needed. Here, we discuss the nail matrix removal technique in 2 cases of longitudinal melanonychia. The first patient underwent a total nail extraction with partial nail matrix excision of the left big toe. The second patient had a partial transverse proximal nail extraction with the partial nail matrix removal of the left thumb. In each case, we evaluated 2 aspects of the nail plate after at least 6 months. Firstly, we assessed whether the lesion has been completely excised. In both of the above cases, no residual lesion was observed. Secondly, we measured the degree of nail dystrophy by dividing the nail plate into 4 quadrants and the presence of lesion counted as 1 point. In both cases, nail splitting was observed in 2 quadrants of the nail plate. In order to minimize nail dystrophic change after nail matrix surgery, we used partial nail matrix shave excision. We herein report the importance of understanding the normal structure and pathology of the nail matrix and that nail matrix shave excision is the proper method for evaluating longitudinal melanonychia.