Unilateral Proptosis Mimicking an Eye Tumour: A Case Report

We report the case of a 56-year-old woman who presented to the Emergency Department with unilateral exophthalmos of the left eye, accompanied by recurrent bitemporal headache. Her past medical history was significant for hypertension, ischemic heart disease, anxiety, depression, and obesity. On clinical examination, the patient was hemodynamically stable, alert, and fully oriented. A brief neurological assessment revealed no focal deficits. Initial laboratory investigations, including complete blood count, serum electrolytes, and coagulation profile, were within normal limits. D-dimer levels were negative. A contrast-enhanced cranial computed tomography (CT) scan ruled out both intracranial space-occupying lesions and cerebral venous sinus thrombosis. Orbital magnetic resonance imaging (MRI) excluded any primary orbital pathology. Endocrine evaluation of the hypothalamic-pituitary-thyroid axis revealed a suppressed thyroid-stimulating hormone (TSH) level of 0.010 mUI/L (reference range: 0.27-4.20 mUI/L) and a free T4 level of 21.59 pmol/L (reference range, adjusted for age and sex: 8.24-21.0 pmol/L). Given the suspicion of Graves-Basedow disease with atypical unilateral ocular involvement, an autoimmune panel was performed. TSH receptor antibodies (TRAb) were markedly elevated at 11.0 U/L (reference range: 0-1.8 U/L), confirming the diagnosis of Graves' disease. Graves' disease is an autoimmune thyroid disorder that typically presents with bilateral exophthalmos due to inflammatory changes and expansion of the extraocular muscles and orbital adipose tissue. However, unilateral exophthalmos, although uncommon, can occur as a manifestation of Graves' orbitopathy.