Introduction: First described by Meyes in 1898, and the subsequent naming of the entity was by Benjamin in 1918. Pneumosinus dilatans, a rare condition, is an abnormal dilatation of one or more of the paranasal sinuses and must be included in the differential diagnosis of expansile lesions of the sinonasal tract. The frontal and sphenoid sinuses are the most frequently involved sites.

Case report: We present the case of a 17-year-old woman with a 1-year history of right nasal obstruction and facial asymmetry, elicited by rapid changes in atmospheric pressure. Computed tomography (CT) detailed an abnormal expansion of the right maxillary sinus resulting from a process of hyperpneumatization with no evidence of bone erosion, leading to the diagnosis of Pneumosinus dilatans. A review of the literature along with possible etiological mechanisms is presented in this report.

Results: Under general anesthesia, the patient underwent restoration of permanent pressure equilibrium in the right maxillary sinus and improvement in the patency of the nasal fossa were achieved by functional endoscopic sinus surgery of the maxillary sinus by an endoscopic approach, the facial asymmetry was corrected by a sublabial incision with satisfactory results.

Conclusion: The aim of Pneumosinus dilatans treatment is to re-establish a permanent pressure equilibrium in the involved sinus and to correct the possible facial deformities.

Conflict of interest : None declared.