Restrictive strabismus caused by infantile myositis masquerading as Duane retraction syndrome.

We report a rare case of restrictive strabismus in a pediatric patient who was initially misdiagnosed with Duane retraction syndrome (DRS) because she had large-angle exotropia, restricted adduction, globe retraction, narrowing of the palpebral fissure, and downshoot on attempted adduction. Notably, the parents first observed strabismus at 12 months of age, with photographs taken before 6 months of age revealing no ocular misalignment. Despite the absence of typical inflammatory signs, the temporal discrepancy, characterized by delayed onset inconsistent with congenital DRS, prompted further investigation. Subsequent magnetic resonance imaging demonstrated no typical appearances of DRS or other intracranial abnormalities but revealed fusiform enlargement of the lateral rectus muscle, raising suspicion of orbital myositis. Surgical exploration confirmed fibrosis of the lateral rectus muscle. Strabismus surgery involving recession of the fibrotic lateral rectus muscle resulted in improved alignment and motility.