Hypertrophy of the abductor hallicus muscle: an unusual congenital foot mass.

A rare case of an isolated congenital muscle hypertrophy involving the abductor hallicus muscle is presented. Although the entity has not been well described previously, it should be entertained in the different diagnoses of medial childhood foot masses. Presently, the diagnoses of such masses should be made more easily with the widespread availability of magnetic resonance imaging. Treatment is generally straightforward, consisting of observation alone, versus partial or total excision, as dictated by the operative findings and previous functional impairment.