An unusual presentation of Trevor's disease at the ankle joint: Involvement of both medial and lateral epiphyses.

INTRODUCTION: Trevor's disease, also known as dyplasia epiphysealis hemimelica, is characterised by osteochondromas arising from epiphyses. The disease typically affects one side of an epiphysis (usually the medial side).

CASE PRESENTATION: A case in whom both the medial and lateral sides of the epiphysis were involved is described. Thus, the use of the descriptor "hemimelica" is not always appropriate.

CONCLUSION: Although rare, Trevor's disease should be kept in mind during the differential diagnosis of patients with ankle pain and a mass. Other possible joints should be examined to explore multiple involvement. Surgical treatment, only on lesions causing impingements, may improve functional status and reduce pain.