Combination of pleuroparenchymal fibroelastosis with non-specific interstitial pneumonia and bronchiolitis obliterans as a complication of hematopoietic stem cell transplantation — Clues to a potential mechanism

Pleuroparenchymal fibroelastosis (PPFE) is a newly described entity of interstitial lung disease, which has been recently recognized as a rare complication of bone marrow transplantation. We report a case of 30-year-old man who developed a unique combination of pleuroparenchymal fibroelastosis with cellular and fibrotic non-specific interstitial pneumonia (NSIP) and bronchiolitis obliterans (BO) sixteen years after hematopoietic stem cell transplantation. Histological examination revealed almost exclusive infiltration of CD3-positive T lymphocytes associated with lymphoepithelial lesions and multi-focal denudation of covering epithelial cells in all components. This case suggests PPFE, NSIP, and BO might be conditions of the same spectrum, pathogenetically related to chronic graft-versus-host disease. Immunostaining for CD3 and CD20 in transbronchial lung biopsies may be helpful for identifying graft-versus-host-driven interstitial lung disease.