Idiopathic orbital myositis in a pregnant woman.

A case of a 29-year-old woman who presented at 25 weeks' gestation with acute onset of painful diplopia and periorbital swelling is presented. Following further investigation, a diagnosis of idiopathic acute lateral rectus myositis was established. Her condition resolved following a 4-week course of oral prednisolone without recurrence. A healthy female was delivered at 40 weeks' gestation. The presenting features, differential diagnosis, treatment and course of orbital myositis are discussed.