Adjuvant Steroid Outcomes in Idiopathic Subglottic Stenosis

1. Diagnosis of iSGS following the NoAAC criteria which involves ruling out known causes for airway stenosis. Participants may be newly diagnosed or carry an existing diagnosis of iSGS;
2. Age Range: 18 years to 80 years old at the time of consent;
3. Sex distribution: all eligible men and women will be included, and no one will be excluded;
4. Have a life expectancy of ≥6 months; and,
5. ECOG performance status of 0 or 1.

Exclusion Criteria:

1. History of subglottic stenosis from identifiable cause (not idiopathic), including any of the below clinical criteria:

   1. Prolonged endotracheal intubation or tracheostomy (intervention greater than 7 days immediately prior to diagnosis of subglottic stenosis);
   2. External physical trauma (including but not limited to blunt, penetration, chemical, or thermal injury) that causes injury to the subglottis;
   3. Clinical diagnosis of granulomatosis with polyangiitis (GPA);
   4. Radiation exposure to the neck;
   5. Complications resulting from the Index Procedure, including needing an endotracheal tube or tracheostomy immediately following surgery or a perforation of the trachea;
2. Current or previous treatment with SILSI;

3. Use of systemic corticosteroids (oral, intravenous, or intramuscular glucocorticoids), regardless of indication, within 7 days before triamcinolone administration;

   1. Local administration of corticosteroids (ophthalmic, intranasal, inhaled) is not prohibited. However, the administration of intraarticular corticosteroids during the Study Drug Dosing phase is not recommended due to potential increased risk of infection.
   2. Intralesional administration, in a site other than the subglottis, of corticosteroids should be discussed with the site PI before enrollment.
   3. Use of inhaled steroids is permitted during the study if the participant was taking at the time of consent, and no new inhaled steroids can be started while enrolled in the study.
4. Intraarticular corticosteroids during the Study Drug Dosing phase due to potential increased risk of infection;
5. Use of anticoagulants other than aspirin (daily aspirin dose should not exceed 81mg);
6. Pulmonary disease including interstitial lung disease or COPD/emphysema;
7. Systemic infection requiring treatment with antibiotics, antifungal, or antiviral agents within 21 days of Enrollment;
8. Poorly controlled diabetes as defined by a HbA1C value greater or equal to 8.0 in the last 180 days;
9. Participants with active cancer or a history of cancer in the last 5 years prior to enrollment, except for squamous or basal cell carcinoma of the skin;
10. Participation in any clinical trial involving an investigational drug or device, within four weeks, or 5 half-lives of the investigational agent (whichever time point is longer) prior to enrollment or during this trial participation;
11. Active autoimmune disease requiring systemic treatment;
12. History of solid organ transplant due to use of immunosuppression;
13. Contraindication to any aspect of the index procedure;
14. Inability to tolerate in-office SILSI procedure;
15. Contraindication, hypersensitivity, or history of intolerance to oral or injectable steroids;

16. Contraindication to SMOFlipid including any of the below:

    1. Severe lipid metabolism disorders characterized by hypertriglyceridemia (greater than 500 mg/dL);
    2. Hypersensitivity to eggs, soybean, peanut protein, or any active ingredient in SMOFlipid;
    3. History of intolerance to SMOFlipid;
17. Participants with known, suspected, or plan for becoming pregnant in the next 6 months after the index procedure, or participants who are breastfeeding;
18. NYHA class II-IV heart failure within the past 6 months prior to Enrollment;
19. History of angioedema;
20. Lack of capacity to consent;
21. Alcohol or substance abuse or dependence in the past 6 months prior to Enrollment;
22. Participants who for any reason may not complete the study as judged by the PI;
23. Participants planning to move to another city or state for 6 months after the Index Procedure;
24. Not able to undergo phlebotomy as reported by the participant or determined by the study coordinator or physician.
25. The presence of a medical condition, lab test result, and/or use of a medication and/or any substance, individually or in aggregate, that in the judgement of the site investigator could impair study participation.