Images in Clinical Medicine

Subungual Exostosis

Alexandre Campanelli, M.D., and Luca Borradori, M.D.

N Engl J Med 2008; 359:e31December 18, 2008

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Article

A 12-year-old girl with an unremarkable history was evaluated for a nodule of the lateral nail fold on the right hallux that had been present for 3 months (Panel A). The lesion, which was initially believed to be a wart, was treated with a topical salicylic acid preparation, with no improvement. The nodule measured 10 mm in diameter, and the distal nail plate showed onycholysis and had been destroyed. A radiograph revealed a calcifying projection on the dorsolateral part of the distal phalanx, continuous with the underlying bone (Panel B), the features of which were consistent with a subungual exostosis. The exostosis was resected, and light-microscopical studies of the resected tumor showed a mature trabecular bone covered by hyaline fibrocartilage tissue (Panel C). Subungual exostosis is a benign osteocartilaginous tumor. It occurs predominantly in children and young adults and often affects the great toe. It has been thought to reflect a reactive metaplasia resulting from microtrauma, but its exact pathogenesis is unclear. In this patient, no clinical problems were detected after 3 years of follow-up.

Alexandre Campanelli, M.D.
Geneva University Hospital, CH-1211 Geneva, Switzerland

Luca Borradori, M.D.
Bern University Hospital, CH-3010 Bern, Switzerland