Background: Sarcoidosis is considered a T-helper (Th) 1 related disease, but a transition from Th1 to Th2 pathway activation has been postulated in chronic pulmonary sarcoidosis (PS) evolved into fibrosis. Fraction of exhaled nitric oxide (FENO) is a marker of Th2 airway inflammation, but alveolar concentration of nitric oxide (CANO) can be measured to assess Th2 inflammation in the periphery of the lung.
Aim of the study: The aim of this cross-sectional observational study was to evaluate the usefulness of CANO as a biomarker of fibrosis in patients with PS.
Methods: We assessed FENO and CANO in patients with PS evolved into lung fibrosis (LF; N=20) and without LF (N=20). Clinical data, as long as respiratory function tests, were also analyzed.
Results: Patients with LF were older than the others (59.3 vs 50.8 years, p<0.01), with more respiratory symptoms and a history of more sarcoidosis relapses (75% vs 35%, p=0.02). The presence of LF was highlighted by a reduction in DLCO% (63.4% vs 79.3%, p<0.01), but not in lung volumes. FENO (25 ppb vs 29.4 ppb, p=0.34) and CANO (5 ppb vs 4.1 ppb, p=0.49) levels did not differ between patients with or without LF, even when dividing them according to steroid therapy. Intriguingly, PF patients also manifested greater airflow limitation and air trapping, with decreased FEV1 (78.5%pred vs 95.7%pred, p=0.01) and Tiffeneau index (67.2% vs 76.3%, p=0.02), as well as increased Motley index (36.3% vs 30.7%, p<0.01).
Conclusions: This pilot study warrants future work with larger samples in order to evaluate the measurement of CANO in patients with fibrosing stage in PS. Airflow limitation can significantly characterize LF in PS.