Introduced in the early 1970s for treatment of aplastic anemia and leukemia, bone marrow transplantation offers potentially effective treatment for a growing number of patients. The procedure is now recognized as therapeutic for an increasing number of diseases. Furthermore, advances in transplant immunobiology, supportive care, and prevention of graft-versus-host disease, coupled with the availability of suitable donors, make the technique both effective and feasible. In 1990 more than 5,500 patients received allogeneic marrow transplants from matched or partially matched family members, and more than 5,000 autologous transplant procedures were performed. The recent creation of the National Marrow Donor Program (NMDP), which currently lists more than 600,000 potential donors, has made identification of unrelated phenotypically HLA-identical donors possible for patients who do not have suitable donors among family members. It is estimated that more than 500 unrelated transplants will be performed in 1992.
Despite these encouraging developments, transplantation-related complications, especially those involving the lung, have limited the success of bone marrow transplantation. Interstitial pneumonitis accounts for more than 40% of transplantation-related deaths in most large series. Of these pneumonias, approximately half are noninfectious idiopathic pneumonia, herein referred to as idiopathic pneumonia syndrome (IPS).
Although IPS is an important clinical entity, progress in understanding the pathogenesis of IPS has been limited. The lack of progress is partly due to different definitions of the disease, different diagnostic criteria, and the relatively small number of patients studied at most centers. However, our understanding of related areas that may be pertinent to the problem of IPS has progressed. For example, there have been major advances in basic immunology, radiation biology, the biology of inflammation, and the role of specific cytokines. More is known about cellular and molecular mechanisms of lung injury and repair. Improved diagnostic procedures to identify infectious causes of lung disease are now becoming available. The applicability of this emerging knowledge, including the therapeutic potential of anti-inflammatory and immunomodulating drugs to the problem of IPS, has not been fully explored.
A workshop sponsored by the Division of Lung Diseases and the Division of Blood Diseases and Resources, National Heart, Lung, and Blood Institute, National Institutes of Health, was held in September 1991 to summarize the state of knowledge regarding IPS. Recent clinical observations and developments in cellular and molecular mechanisms of tissue injury that relate to the pathogenesis of IPS were discussed with the goal of identifying promising directions for future research.