ILD may be caused by myriad etiologies with differing prognoses and natural history. Indeed, multiple factors may injure the alveolar epithelium and initiate the development of ILD [25] . The initiating injury can be introduced through the airways and the circulation, or can occur as a result of sensitization. Consequently, the mechanisms underlying disease progression will be influenced by the causative event as well as by the host and the environment. These mechanisms are developed through interactions of multiple pathways, which include apoptotic pathways, developmental pathways, and endoplasmic reticulum (ER) associated pathways ( Figure 1 ).