Small airways and airspace inflammation and injury distinguish lung histopathology in deployed military personnel from healthy and diseased lungs

The link between military deployment to Southwest Asia and Afghanistan, and the risk for lung disease, including bronchiolitis, is increasingly well-recognized. However, histopathologic features that distinguish deployment-related lung diseases from other diseases affecting the small airways and airspaces are uncertain. A computer-based scoring system was developed to characterize surgical lung biopsy findings in 65 soldiers with persistent respiratory symptoms following military deployment (“deployers”). Deployer lung biopsies were compared to those from 8 patients with chronic hypersensitivity pneumonitis (cHP), 10 with smoking-related respiratory bronchiolitis, 11 with autoimmune or post-transplant obliterative bronchiolitis, and 10 normal donor lungs. Upper, middle, and lower lobe-specific findings in deployer samples were analyzed to inform optimum biopsy location choice for future patients. Surgical lung biopsies from symptomatic deployed military service members were distinguished by a combination of small airways abnormalities including smooth muscle hypertrophy (SMH), peribronchiolar metaplasia (PBM), and lymphocytic inflammation, often with constrictive/obliterative (C/O) and/or respiratory bronchiolitis (43.1%), granulomatous inflammation (38.5%), and moderate/severe emphysema (46.2%, mainly in nonsmokers). Lymphocytic pleural inflammation was common (89.2%), and vascular abnormalities occurred in nearly one-third. Histopathologic features in deployers were most strongly overlapping with cases of cHP, both showing granulomatous inflammation, PBM, and emphysema. SMH along with C/O and respiratory bronchiolitis were common in deployers but not in cHP cases. In deployers, there were significantly higher odds of small airways injury in the lower lobe compared with upper lobe samples.