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Longitudinal melanonychia

Dr. Mona Abdel-Halim


It was last week when I accidentally discovered a longitudinal band of melanonychia in my left little toe. Surprisingly, this was in the evening of a long day at work that included a signing out of a case of in transit metastasis of acral lentiginous melanoma!!!!

Needless to say that my first decision was to arrange with my colleague, who is excellent in nail biopsies, to do a nail biopsy immediately. With the image of a metastatic acral lentiginous melanoma, I could not think of something else !!! He suggested starting by dermoscopy. I had my self examined by a colleague who is expert in dermoscopy, who re-assured me about it. A faint background of pigmentation with thin very light brown parallel lines that are regular in color, thickness and spacing, consistent with melanocyte activation.

This experience made me read some nice articles about longitudinal melanonychia. Although subungual melanoma may start as a band of melanonychia, not every longitudinal melanonychia is a subungual melanoma. It might reflect melanocyte activation, nail lentigo or nail nevus. Interestingly, melanocyte activation which is just increased activity of melanocytes with subsequent increased pigmentation of the matrix, has been found to be caused by shoe friction (frictional longitudinal melanonychia) which was found typically to affect the 4th and 5th toes !!! As in my case !!! Dermoscopy plays an important role in evaluating these cases and in picking up those cases that really need a biopsy. Will be following up my lesion and will feed you back if I needed to take a biopsy one day !!!! I might then show it to you all !!!

Here are a couple of informative articles about the issue.

[center][b]Tosti A. et al. : Dealing with melanonychia. Sem Cutan Med and Surg 2009; 28: 49-54[/b][/center]

[center][b]Roger S. et al.: Dermoscopic examination of nail pigmentation. Arch Dermatol 2002; 138: 1327-33[/b][/center]

[center][b]Jellinek N.: Nail matrix biopsy of longitudinal melanonychia:Diagnostic Algorithm including the matrix shave biopsy. J Am Acad Dermatol 2007; 56: 803-10[/b][/center]


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