A narrowing of the trachea directly inferior to the vocal cords
Idiopathic (more likely to affect females)
Congenital abnormality in newborns
Past mechanical trauma to the airway (intubation or surgery)
Autoimmune disorders
Wegener's granulomatosis/ GPA - Approximately 36% of patients with GPA develop<unk>  
Rheumatoid arthritis
Sarcoidosis
Subglottic stenosis
Larynx fracture
Tracheomalacia
Tracheobronchial tear/injury
Bacterial tracheitis
Thyroid gland injury/trauma
Retropharyngeal abscess
Tracheal injury