Acute, Highly Asymmetric Thyroid Eye Disease Mimicking Orbital Cellulitis: A Case Report

Abstract

Background: Thyroid eye disease is an immune-mediated orbital disorder that may cause proptosis, eyelid oedema, chemosis, and restricted ocular motility. Acute, markedly asymmetric presentations can closely resemble orbital cellulitis, making prompt clinical assessment and orbital imaging essential for accurate diagnosis. Aims: The study aims to describe an acute, highly asymmetric presentation of thyroid eye disease (TED) in an elderly woman with treated hyperthyroidism and to emphasise the role of emergency orbital imaging in differentiating TED from orbital cellulitis. Presentation of Case: A woman in her late seventies who was receiving thiamazole 10 mg twice daily and propranolol 20 mg daily for hyperthyroidism presented with painful bilateral proptosis that was markedly more pronounced in the left eye. The left eye showed eyelid oedema, conjunctival hyperaemia, chemosis, and limited ocular motility. The anterior segment was quiet, and fundus examination was normal. No fever was documented in the emergency record, and the complete blood count and C-reactive protein level were normal. Urgent orbito-cerebral computed tomography demonstrated bilateral grade 1 proptosis and bilateral enlargement of the extraocular muscle bellies, with relative sparing of the anterior tendinous insertions and no reported orbital collection. These findings supported active, left-predominant TED rather than infectious orbital cellulitis. Antithyroid therapy was continued, and systemic corticosteroids were administered, resulting in improvement in pain, chemosis, conjunctival inflammation, and eyelid oedema. Discussion: Asymmetric, painful proptosis may mimic infectious orbital disease. In this case, the thyroid history, bilateral CT involvement, tendon-sparing myopathy, normal inflammatory markers, and absence of an orbital collection were decisive diagnostic clues. Conclusion: TED should be considered in patients with thyroid dysfunction who present with painful or asymmetric proptosis. Prompt imaging and multidisciplinary care are essential to exclude vision-threatening and infectious conditions.