subunguale Exostosen

Subungual exostoses are benign osteocartilaginous tumors that occur beneath the nail bed.

Epidemiology

These lesions are most commonly found in children and young adolescents .

Clinical presentation

Although they can be found beneath any nail, they most commonly affect the big (first) toe . In the majority of cases, patients are able to give a history of trauma or infection to the affected toe . Presentation is usually with pain and swelling. There may be ulceration of the overlying nail .

Pathology

Subungual exostoses probably result from metaplasia in mechanical irritations or diseases of the nailbed although the precise etiology is unknown .  The lesion is composed of mature fibrocartilaginous tissue and bone and resembles callus .

Radiographic features

These lesions are osseous although in some cases they can grow very rapidly and mimic a sarcoma . They are almost invariably connected to the underlying bone. Although usually appear as well-circumscribed bone, they lack clear contiguity of both the medullary cavity and cortex, which helps to distinguish them from osteochondromas.

Treatment and prognosis

These lesions are benign. Resection of the exostosis and curettage of the underlying bone is curative .

Differential diagnosis

On radiographs consider: