Interstitial inflammatory lesions of the pulmonary allograft: a retrospective analysis of 2697 transbronchial biopsies.

BACKGROUND: Parenchymal and bronchial inflammatory and fibrotic lesions other than acute cellular rejection (ACR) and lymphocytic bronchiolitis are prevalent; however, the context in which they appear is unknown, and often no specific treatment is instigated.
OBJECTIVES: To describe the prevalence, incidence and possible associations between commonly identified inflammatory and fibrotic lesions in the pulmonary allograft.
METHODS: Retrospective chart review of all transbronchial biopsies performed within the first 2 years of 299 lung-transplanted patients in the period 1996 to 2006.
RESULTS: A total of 2697 biopsies were evaluated corresponding to a mean of 6+/-2 (median 8) completed schedules per patient. Diffuse alveolar damage (DAD) was the second most common histological finding within the first 2 weeks after transplantation. The peak prevalence of bronchiolitis obliterans organizing pneumonia (BOOP) and interstitial pneumonitis occurred at 4 to 6 weeks, and 6 to 12 weeks, respectively. There was a steady increase in the cumulative proportion of patients with fibrosis and bronchiolitis obliterans, at each successive scheduled surveillance time point beyond 3 months posttransplantation. The strongest histological correlations were between ACR and lymphocytic bronchiolitis (OR 5.1, P<0.0001) or interstitial fibrosis (OR 3.2, P<0.0001). Patients with interstitial pneumonitis and pulmonary hemosiderosis were also more likely to demonstrate the finding of interstitial fibrosis (OR 3.0 and 3.7, P<0.0001, respectively). Acute cellular rejection was not associated with DAD, and patients with lymphocytic bronchiolitis were not more likely to demonstrate features of organizing pneumonia (DAD or BOOP).
CONCLUSIONS: Histologic findings of ACR, lymphocytic bronchiolitis, BOOP, and interstitial pneumonitis were directly associated with the development of interstitial fibrosis and bronchiolitis obliterans.