Osteoid osteoma of the distal phalanx of the thumb.

An osteoid osteoma of the distal phalanx of the thumb in a 14-year-old girl is described. Apart from the rare site of the lesion, other unusual features included early closure of the epiphyseal plate, enlargement of the involved segment of the thumb, and hypertrophy of the nailbed. The radiographic appearance was unusual in that it simulated a soft tissue mass eroding the bone from without.