| Allergic rhinitis |
| Chronic exposure to environmental irritants or ciliostatic substances (eg, tobacco smoke) |
| Immunodeficiency states (especially defects in antibody production or function) |
| Defects in mucociliary clearance (eg, cystic fibrosis and primary ciliary dyskinesia) |
| Recurrent viral upper respiratory tract infections |
| Systemic disorders (eg, granulomatosis with polyangiitis [Wegener's], eosinophilic granulomatosis with polyangiitis [Churg-Strauss], sarcoidosis) |
| Anatomic abnormalities predisposing to sinus obstruction |
| Iatrogenic (due to complications of repeated sinus surgery) |
