SUBUNGUAL EXOSTOSIS OF THE GREAT TOE IN AN ADOLESCENT: A RARE CAUSE OF PAINFUL NAIL DEFORMITY

Background: Subungual exostosis is an uncommon benign osteocartilaginous lesion arising from the distal phalanx beneath or adjacent to the nail apparatus. It commonly affects the great toe and may cause pain, swelling, progressive nail elevation, onycholysis, and deformity. Because it can mimic other nail-unit disorders, timely clinical and radiological recognition is important to avoid delayed diagnosis and inappropriate treatment. Case Presentation: A 16-year-old male presented with painful swelling of the right great toe. Examination revealed a tender subungual lesion with elevation and deformity of the nail, without significant local infection. Plain radiography demonstrated a bony projection arising from the distal phalanx. Magnetic resonance imaging showed an 8.6 × 4 mm anteromedial subungual bony outgrowth, with no marrow oedema or peri-osseous soft-tissue collection. The lesion was treated by subungual surgical excision with careful nail-bed dissection and complete removal from the distal phalanx. Histopathological examination showed bony tissue with a mature hyaline cartilaginous cap and overlying fibrous perichondrium, marrow elements within the bony stalk, and endochondral ossification at the bone-cartilage junction; the biopsy was reported as showing features consistent with the clinical diagnosis of osteochondroma, with clinicoradiological correlation advised. The nail bed and surrounding tissues were preserved and repaired, and the immediate postoperative course was uncomplicated. Conclusion: Subungual exostosis should be considered in adolescents with persistent great-toe pain, swelling, and progressive nail deformity. Radiography and MRI are valuable for confirming the bony origin and extent of the lesion. Complete excision with meticulous preservation of the nail bed can provide an uncomplicated immediate outcome, although continued follow-up is necessary to detect recurrence and assess long-term nail recovery.