Lower Respiratory Tract Diseases Caused by Common Respiratory Viruses among Stem Cell Transplantation Recipients: A Single Center Experience in Korea

Hong, Kyung-Wook; Choi, Su-Mi; Lee, Dong-Gun; Cho, Sung-Yeon; Lee, Hyo-Jin; Choi, Jae-Ki; Kim, Si-Hyun; Park, Sun Hee; Choi, Jung-Hyun; Yoo, Jin-Hong; Lee, Jong-Wook

In the present study, high-dose steroid usage and lymphopenia were shown to be risk factors for mortality in SCT recipients with CRV-LRDs. Lymphopenia was previously reported as a risk factor for mortality among SCT patients with LRDs caused by influenza or RSV. 6, 13, 19 Additionally, high-dose steroid usage during the 2 weeks preceding a CRV-LRD diagnosis was reported as an independent predictor of mortality among SCT recipients with HPIV-LRDs. 9, 23 It is likely that these two risk factors are associated with a decreased T-cell-mediated immune response. 22 Furthermore, high-dose corticosteroid use is known to be associated with a trend toward delayed viral clearance. 35 Conversely, a few previous studies reported that the use of corticosteroids exerted protective effects against the progression to pneumonia and requirement for mechanical ventilation among SCT recipients with influenza-LRDs, which was hypothesized to occur due to a salutary immunomodulatory effect. 13, 15 There are several limitations of the present study. As this was a retrospective study, there were no standardized guidelines for the screening and treatment of CRV infections. However, to overcome this limitation, only CRV-LRD cases were included. Due to the small number of cases, it was not possible to analyze the risk factors for mortality for individual CRV-LRDs. Another limitation was that it was difficult to determine whether the fatal outcome was solely attributable to the CRV or due to a combination of the CRV and co-pathogens. However, precise discrimination of the pathogen would likely have been meaningless, since damage to the respiratory epithelium as a result of a CRV infection may have been the key factor that facilitated the occurrence of superinfections. 9 Recent studies showed that viral nucleic acid was detected in the bloodstream more frequently among SCT recipients with LRDs caused by influenza, RSV, HAdV, and HMPV, and that this was associated with increased mortality rates. [36] [37] [38] Therefore, viral nucleic acid detection in the bloodstream of SCT recipients with CRV-LRDs could be used to predict disease severity, poor outcome, and the need for intensified antiviral treatment in the future.