RESUMO
Pneumosinus dilatans (PD) is a rare disorder of unknown etiology which consists of an abnormal dilatation of one or more paranasal air sinuses without radiological evidence of localized mucous membrane alterations, hyperostosis, or bony erosion. Sinus walls are therefore of normal thickness. The enlargement of the bone may be generalized or focal, and apart from the aesthetic problem it carries, it is important to bear in mind the possible functional consequences it may imply. Although PD is usually a benign asymptomatic condition, some patients may develop progressive neurological signs and symptoms caused by the expanded sinuses. We herein present the case of a 12-year-old boy who had been referred to the Ophthalmology Department, complaining of a progressive and painless exophthalmos of his left eye, developed during 1 year. The cause was unknown and there were no functional problems. Computed tomography and magnetic resonance showed a large pneumatized ethmoidal sinus and confirmed the resulting proptosis. We asked the Ear Nose and Throat (ENT) department for a further examination, and finally, the patient was taken to the operating room, where the left ethmoidal sinus was exposed to an endoscopic endonasal technique; in particular, a maxillary and frontal endoscopic antrostomy ethmoidectomy was performed. Excellent results were obtained and the patient had no complaints. Currently, he remains well after a 16-month postoperative period.