Perivascular inflammation in pulmonary infections: implications for the diagnosis of lung rejection

Transbronchial lung biopsy is rapidly becoming the procedure of choice for diagnosing lung rejection, and diagnostic criteria are evolving. The presence of perivascular lymphocytic infiltrates has been stated to be sufficient for this diagnosis, although the specificity of this histologic finding has not been determined. In a review of 42 cases of pneumocystis and cytomegalovirus pneumonia diagnosed by open (33 cases) and by transbronchial lung biopsy (nine cases) from immunosuppressed patients (excluding those with underlying non-Hodgkin's lymphoma), perivascular lymphocytic infiltrates similar to those observed in lung rejection were identified in 26% of cases overall, 21% of pneumocystis cases (n = 33), 42% of cytomegalovirus cases (n = 7), and 50% of cases of combined pneumocystis and cytomegalovirus pneumonia (n = 2). The presence of a perivascular infiltrate did not correlate with the pattern of lung histology (diffuse alveolar damage, mononuclear interstitial pneumonia, or organizing pneumonia) or with overall cellularity of the specimens. As cytomegalovirus and pneumocystis are the two most common nonbacterial pathogens in lung transplant recipients, these findings support a multimodal approach to the diagnosis of lung rejection and argue for caution in interpreting the presence of perivascular inflammation on transbronchial biopsies in this setting until a diagnosis of infection is excluded.