C-Reactive Protein Serum Values in Idiopathic and Autoimmune Subglottic Stenosis

Idiopathic and granulomatosis with polyangiitis (GPA)-related subglottic stenosis (SGS) are considered distinct immune-mediated inflammatory disorders. Limited data exist on serum inflammatory markers, specifically C-Reactive Protein (CRP), for SGS diagnosis, differentiation, and prognostication. The study objective was the characterization of CRP levels in idiopathic (iSGS) and GPA-SGS to assess CRP's ability to distinguish SGS subtypes and predict SGS progression and recurrence.

Retrospective review of patients with idiopathic or GPA-SGS from 2007 to 2024 at a single institution. Surgery-free interval (SFI) was calculated as the time between surgical interventions. Statistical analysis included independent t-tests, chi-squared, and univariate linear regression.

59 iSGS and 47 GPA-SGS patients were included. CRP was elevated in 36% of iSGS and 49% of GPA-SGS patients (0.0.6 mg/dL). Mean maximum CRP was 2.7 mg/dL lower in iSGS compared to anti-neutrophil cytoplasmic antibody (ANCA)-positive GPA-SGS (p = 0.035). The maximum CRP in iSGS was 3.6 mg/dL, while 10 (21%) GPA patients had CRPs greater than 3.6 mg/dL (max = 31 mg/dL). ANCA-negative GPA-SGS mean CRP was not significantly different than iSGS or ANCA-positive GPA-SGS. CRP and SFI did not correlate on univariate linear analysis.

Mild elevation of CRP is common in SGS patients. High CRP levels are more frequent in GPA-SGS, potentially aiding clinical differentiation of etiologies. However, CRP at presentation does not appear to correlate with disease recurrence in iSGS or GPA-related SGS, limiting its value as a biomarker and prognostic tool.