- Tracheomalacia: Cartilagenous weakness that occurs for unclear reason
- Stenosis related to prior injury, intubation (often prolonged), surgery, tracheostomy
- Autoimmune/Inflammatory processes: relapsing polychondritis, granulomatosis w/polyangiitis, RA, sarcoid, other
- Extrinsic compression from benign processes: Profound thyromegaly, fibrosing mediastinitis, other
- Symptoms may be related to primary process
- Stridor, loudest when listening over trachea
- Other findings may be related to primary process (if one exits)