Abstract
Tracheobronchopathia osteochondroplastica (TPO) is a very rare, benign disorder involving the lumen of the trachea-bronchial tree. However, its etiology is unknown. In our first case, observation for several years showed that TPO worsened as interstitial lung disease was aggravated. In the second case, the lung parenchymal lesion on computed tomography (CT) was found to be compatible with interstitial lung abnormality (ILA). We believe that our cases suggest a common pathogenetic relationship between TPO and fibrotic interstitial lung disease. TGF-β is likely a common factor in the pathogenesis of TPO and fibrotic interstitial lung disease.