Background: Orbital findings such as cellulitis, ophthalmoplegia, and proptosis are possible complications of sinusitis. Acute sinusitis can also cause a conjunctival cyst-like lesion induced by severe chemosis; however, it is an uncommon complication.

We report the case of a 53-year-old man who presented to our facility's emergency department. The patient complained of orbital discomfort resulting from an inability to close both eyes, and orbital discharge, accompanied by general weakness. On physical examination, cyst-like-appearing lesions with erythema of the eyelids were identified bilaterally and initially misdiagnosed as inflammatory lesions of the orbital area. However, orbital pathology was excluded by the ophthalmologist, and it was found that the patient had bilateral pansinusitis on the imaging studies. It was suspected that the sinusitis was responsible for the ocular symptoms. The patient was treated with emergent endoscopic sinus surgery, and the symptoms were promptly relieved.

Although it is well known that orbital complications of sinusitis can occur, a conjunctival cyst-like-appearing lesion induced by severe chemosis is uncommon and is difficult to diagnose at first sight. Emergent surgical drainage is needed to prevent permanent orbital damage and other sinusitis-related complications. Therefore, recognizing the unique clinical presentation of a conjunctival cyst-like lesion resulting from severe chemosis is the key to appropriate diagnosis and management.