An infant with idiopathic orbital myositis poorly responsive to steroid therapy: a case report.

A 9-month-old girl developed subacute limited adduction of the left eye, presenting with blepharoptosis. An orbital magnetic resonance imaging (MRI) 2 months after the onset revealed swelling of the left lateral rectus muscle, with increased intensity on T2-weighted images with fat saturation, which was enhanced with gadolinium. She was diagnosed with idiopathic orbital myositis based on history, physical examination, and MRI findings. Swelling of the left lateral rectus muscle was partially reduced by pulse steroid therapy. This is the first reported case of an infant orbital pseudotumor with clinical and MRI findings consistent with subacute orbital myositis. We propose that a fibrotic change of the orbital muscle may occur during a subacute course and would be incompletely responsive to steroid therapy.