Both of these series suggest the possibility that IPF is a thrombophilic state. As noted by Nathan et al, past studies3
have also suggested an abnormally high rate of pulmonary embolism in IPF, and the rates in these studies likely were underestimates given the difficulty of diagnosis of pulmonary embolism. Endothelial injury is hypothesized to occur as part of the pathogenesis of IPF. While the primary vascular bed injured in IPF may be the pulmonary bed, leading to local damage resulting in lung fibrosis, this does not exclude the possibility of more generalized endothelial injury occurring in this disease. If damage to the endothelium in, for example, the deep venous system were also to occur, mediated by the circulating factors discovered in the patients of Magro et al,2
this would help explain a predisposition to thrombosis in this disease. Endothelial injury and hypercoagulability, as denoted by the presence of antiphospholipid antibodies, would be present, constituting two of the essential components of Virchow’s triad of thrombosis.