Abstract
<title>Abstract</title> <p>Background Idiopathic orbital inflammatory disease (IOID) and ocular myasthenia gravis (OMG) are distinct disorders. Their coexistence is extremely rare, particularly their simultaneous bilateral presentation, which may obscure diagnosis and delay the recognition of a concomitant disease. Case presentation: We report a 55-year-old woman who presented with bilateral periorbital pain, swelling, redness, and blurred vision associated with severe restriction of extraocular motility and frozen globe. Orbital computed tomography demonstrated bilateral enlargement of all extraocular muscles with tendon involvement, leading to an initial diagnosis of IOID. Intravenous methylprednisolone alleviated orbital inflammation; however, persistent ophthalmoplegia, bilateral ptosis, and binocular diplopia became evident. Further investigations revealed elevated anti-acetylcholine receptor antibody levels and single-fiber electromyography demonstrated increased jitter, confirming OMG. The patient was treated with corticosteroids, pyridostigmine, and intravenous immunoglobulin. Follow-up imaging later showed the complete resolution of extraocular muscle enlargement despite persistent ptosis and ophthalmoplegia. Conclusions This case highlights the diagnostic challenge of concurrent bilateral IOID and OMG, in which orbital inflammation initially masked the characteristic of OMG. Clinicians should consider coexisting pathology when clinical findings or treatment response cannot be fully explained by a single disease process.</p>