[Validity of immunohistology and in situ hybridization in the differential diagnosis of cytomegalovirus pneumonia and idiopathic interstitial pneumonia after allogenic bone marrow transplantation].

Interstitial pneumonia (IP) is currently the most frequent and severe complication of allogeneic bone marrow transplantation (BMT). Post-BMT-IP is due partially to infection by cytomegalovirus (CMV-IP) and partially to idiopathic induction (IIP). Because of the different therapeutic consequences it is important to distinguish between these two kinds of pneumonia. Therefore, the validity of immunohistochemistry (IHC) and in situ hybridization (ISH) for the differential diagnosis of CMV-IP and IIP was studied. The investigations were performed using postmortem tissue samples (lung) of 23 patients decreased after allogeneic BMT. In 22 of the 23 patients the primary cause of death was IP (CMV 13x, idiopathic 7x, pneumocystis 1x, toxoplasmosis 1x). One patient died from thrombopenic cerebral bleeding. All 3 CMV-detecting systems tested disclosed certain advantages and disadvantages. The sensitivity of routine histology was 12/13 (92.3%), of IHC 13/13 (100%), and of ISH 12/13 (92.3%). The specificity corresponded to the order: ISH greater than IHC greater than histology. The application of ISH and IHC did not change significantly the routine histologic classification of pneumonias into CMV-IP and IIP. The validity of the three procedures used for detecting CMV in patients after allogeneic BMT is discussed in detail.