Pediatric Subungual Exostosis.

Exostosis is a type of benign bone tumor in which trabecular (spongy) bone overgrows its normal border in a nodular pattern. When the growth occurs under the nail bed, it is termed subungual exostosis or Dupuytren exostosis. This condition may mimic other bony abnormalities such as an osteochondroma and may present with nail deformities with or without pain. For this reason, a biopsy of the lesion is necessary to rule out a precancerous growth. In rare cases, pediatric patients may have subungual exostosis, as demonstrated in our case.