'A Down and Out Eye': Case Report of a Primary Ethmoid Mucocele.

Paranasal sinus mucoceles are benign, locally expansile masses of the paranasal sinuses that are lined by epithelial cells. They result from obstruction of sinus ostia. The close proximity of paranasal sinus mucoceles to the orbit and skull base predisposing the patient to significant morbidity. We describe the case of a previously healthy 23-year-old gentleman presenting with a five-day history of unilateral (left) eye pain and swelling with an obvious deformity. There was also no history of trauma or prior surgery. He underwent a CT sinus, which showed near complete opacification of the left anterior ethmoid sinus with bony destruction and obvious displacement of the orbit both laterally and anteriorly. This was assessed as to be in keeping with an ethmoid mucocele. Endoscopic marsupialization has become the preferred surgical approach over obliterative procedures for the treatment of paranasal sinus mucoceles. Primary ethmoid mucocele is an uncommon entity, especially in the absence of prior ear, nose and throat (ENT) complaints, and therefore should remain an important differential when a patient presents with a unilateral swelling causing proptosis.