Lump on a boy's left great toe

• What's the diagnosis? • How would you treat him?

Diagnosis: Subungual exostosis

Though first described in the medical literature in the 1800s, the etiopathology of SE remains unclear. SE may be a true neoplasm, or possibly an aberration of development in endochondral bone formation.³ SE has been associated with the rare hereditary multiple exostosis syndrome, although only four patients of 312 reviewed by Davis and Cohen occurred in that setting.⁴ Patients frequently report antecedent traumas, so SE may be thought of as a reactional osteocartilaginous outgrowth, secondary to mechanical irritation.²

Subungual exostoses frequently develop during adolescence.⁵ In pediatric patients (about 16% of total cases), SE is very rare under 7 years. The ratio of boys to girls is approximately 1:1, and involvement of the hallux is reported in 67% of cases.²

Clinical findings

SE usually presents as an asymptomatic reddish-pink nodule beneath the nail that may become painful as it enlarges. It may also ulcerate or become infected.² Lesions are most commonly located deep to the free edge of the nail. The growth pushes the nail edge and, sometimes, the entire nail upward.⁵

Plane and lateral radiograph digital imaging, which show a sessile or pedunculated expansion of trabecular bone covered with radioluscent cartilage, can confirm the clinical diagnosis. Furthermore, there is no cortical disruption or any abnormality of the distal phalanx.²

Differential diagnosis

Consider warts and all other tumors that commonly occur in a subungual location, including pyogenic granuloma, keratoacathoma, melanotic whitlow, endochodroma, epidermal cyst, glomus tumor, epidermoid inclusion cyst, and subungual hematoma. Other lesions that may occasionally appear in this location include hemangioma, angiokeratoma, sarcoidosis, sarcoma, neurofibroma, and malignancy.⁵

Treatment

Asymptomatic stable lesions need no intervention.³ However, the treatment of painful lesions or those that cause functional impairment remains surgical. Recurrence is common but malignant change is rare.²

Our patient

At a six-month follow-up visit, the nodule was unchanged and asymptomatic. We will continue to follow him clinically, and excise the lesion if it becomes painful or interferes with normal function.