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Beth Israel Deaconess Medical Center Boston, MA
Correspondence to: Matthew D. Jankowich, MD, 50 Park Row West, #314, Providence, RI 02903; e-mail: mjankowi{at}caregroup.harvard.edu
To the Editor:
The recent observation by Nathan et al1 in the May 2003 issue of CHEST of a high rate of pulmonary embolism in patients with idiopathic pulmonary fibrosis (IPF) after lung transplantation is intriguing. A recent report by Magro et al2 of 19 patients with IPF with histologic evidence at open-lung biopsy of microvascular injury along with corresponding immunologic evidence of antiphospholipid antibodies and antiendothelial cell antibodies is of note in light of the findings of Nathan et al.1 In the series of Magro et al,2 4 of the 19 patients had "1 or more episodes of venous thrombosis." All 4 of these patients had a positive lupus anticoagulant; 18 of the 19 patients had evidence of antiphospholipid antibodies. Of interest would be whether any of the patients of Nathan et al1 were tested for antiphospholipid antibodies.
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.
More research into the question of thrombophilia in IPF is needed; particular areas to be addressed would be confirmation of a high prevalence of antiphospholipid antibodies in these patients and whether a subgroup of these patients at particular risk for venous thromboembolism can be identified. Such studies would point to a group of patients that would potentially benefit from anticoagulation in the pretransplant and posttransplant settings.
References
INOVA Fairfax Hospital Fairfax, VA
Correspondence to: Steven D. Nathan, MD, Inova Fairfax Hospital, 3300 Gallows Rd, Falls Church, VA 22042-3300
To the Editor:
We thank the author for his comments, and for bringing to our attention the findings of Magro and associates,1 which were published after our article had been accepted. The article by Magro et al1 describes a finding that provides biological plausibility for our report and is therefore supportive of the fact that the findings of our study were not due to a type I error. This apparent thrombophilic state is more likely a consequence of idiopathic pulmonary fibrosis (IPF) rather than the initiating factor, since the latter would not fit the current hypothesis that IPF is due to recurrent epithelial injury. We agree that the findings of Magro et al1 need to be verified prospectively by other groups and the presence of antiphospholipid antibodies stratified by disease severity. Along these lines, although we did not test any of the patients in our reported series, we have started testing all our new IPF patients prospectively for the presence of this class of antibodies. Depending on the results of such future studies, it may become evident that all patients with suspected IPF should be so tested, not only to stratify them for risk of thromboembolic events, but also as a potential disease marker. If the high prevalence found in the series by Magro et al1 is substantiated, then a case may even be made for empirically administering anticoagulation therapy to all IPF patients.
References
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