Prognostic Impact of Mediastinal Lymph Nodes in Interstitial Lung Diseases: Is Environmental Exposure the Offender?/Reply

Inhaled agents are known to induce a series of lesions in alveolar epithelial cells, causing a biochemical oxidant injury and thereafter an immunological response when healing mechanisms (e.g., inflammation, coagulation, and epithelial repair) are put in place, resulting in pulmonary fibrosis. Based on U.S. death certificates from 1999 to 2003, Pinheiro and colleagues identified three industry categories with potential exposure to wood and metal dust that were associated with statistically significant risk estimates for IPF mortality: fabricated structural metal products (mortality odds ratio [MOR], 1.7 [95% CI, 1.0-3.1]), metal mining (MOR, 2.2 [95% CI, 1.1-4.4]), and wood buildings and mobile homes (MOR, 5.3 [95% CI, 1.2-23.8]) (5). Enlarged MLNs in ILDs may be at least in part a marker of occupational or environmental exposure. [...]we may hypothesize that the prognostic impact of MLNs observed in the study by Adegunsoye and colleagues could be related to the negative effects of unrecognized exposures. Lescoat and colleagues also raise the important issue of chronic heart failure, which may be prevalent in ILD and should be carefully considered when evaluating the impact of novel indices on assessment of clinical outcomes such as hospitalization and mortality. Because it is possible that cardiac disease may at least in part causally mediate the link between MLN enlargement and ILD outcomes (4, 5), we explored the association of NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels with MLN enlargement in our outcome analyses.