Nonbacterial nonfungal pneumonia following marrow transplantation in 100 identical twins.

Pneumonia attributable to causes other than bacterial or fungal infection is a major complication of allogeneic marrow transplantation. In this study, the incidence, mortality, and possible risk factors for the development of nonbacterial, nonfungal pneumonia after 100 syngeneic marrow transplants for hematological malignancy are reviewed and compared with the results found in 351 allogeneic marrow transplants performed during the same time period. Both the incidence and mortality of pneumonia were far lower among syngeneic patients, especially for pneumonia associated with cytomegalovirus. Idiopathic pneumonia, however, occurred with about equal frequency in the two populations. Among twins, an increased incidence of pneumonia was seen in older patients and in those who received chemotherapy in addition to cyclophosphamide and total body irradiation as part of the preparative regimen for transplantation.