Pneumosinus Dilatans: Over 100 Years Without an Etiology

Purpose Pneumosinus dilatans (PD) is a rare pathologic hyperaeration of the paranasal sinuses that causes serious deformation of the overlying bone and soft tissue. The condition occurs most commonly in the frontal sinus of young men who present with different complaints, including cosmetic. More than 100 cases have been reported in the literature since it was first described in 1898; however, the etiology of this condition remains unclear. Materials and Methods A systematic review of all available clinical publications on the subject of PD was conducted in the PubMed electronic database. The resultant articles were grouped based on evidence supporting or refuting various theoretical etiologies to further characterize the condition. Results In total, 134 known cases were reported in 117 articles. Most affected patients were young men in the third decade of life. Only 19 (16.2%) articles offered some form of evidence in support of a particular etiology. The most substantiated etiologies of PD included a “ball-valve” mechanism of sinus outflow obstruction leading to air trapping or a primary fibro-osseous pathologic process that disrupts the cellular milieu. Less substantiated theories included hormonal dysregulation or a spontaneously draining mucocele. No data exist to support causation by gas-forming bacteria. A bimodal distribution of incidence, a younger population (16 to 25 yr), and an older population (36 to 40 yr) might suggest multiple possible etiologies. Conclusions Several theories on the etiology of PD exist, but none have been substantiated by reliable scientific evidence. Standardizing the clinical evaluation, classification, management, and pathologic analysis of patients with PD could aid in elucidating its true etiology.