Subungual Exostosis on the Right Hallux.

Subungual exostosis (SE) is a benign, relatively uncommon bony growth underneath the nails of the distal phalanx of toes or fingers, with a majority on the toes. Clinically, it has two subvariants-protruded and nonprotruded growths from nail plates-which are treated differently. In this article, we report a case of protruded SE in a teenager with illustrative surgical excision. A 15-year-old boy presented with a painful growth on his right great toe of 6 months' duration. Physical examination revealed a 1-cm-diameter, solid, erythematous, rough, irregular growth penetrating through the skin along the dorsolateral nail bed of the right hallux with deformity of the lateral nail plate. Radiographs showed an elevated mass over the distal phalanx of the right lateral hallux. The mass was surgically excised and histopathologic examination confirmed the diagnosis of SE. The patient had no relapse or recurrence at follow-ups of 6 and 18 months. Subungual exostosis is a relatively uncommon bony growth in the toes. Radiography is favored for the diagnosis. Complete surgical excision is the optimal treatment, with rare recurrence. It needs to be differentiated from other bony lesions, including bizarre parosteal osteochondromatous proliferation, myositis ossificans, fibro-osseous pseudotumor, osteochondroma, and enchondroma.