Viral encephalitis after haplo‐identical hematopoietic stem cell transplantation: Causative viral spectrum, characteristics, and risk factors

To retrospectively identify characteristics and risk factors of viral encephalitis (VE) in patients who underwent a haplo-identical hematopoietic stem cell transplant (HSCT).A nested case-control study was designed. Cases with VE and controls were identified from a cohort composed of 1274 patients who underwent a haplo-identical HSCT from 2012 to 2015.VE was identified in 30 patients (2.4%). The median time from HSCT to diagnosis was 144.5 days. The viruses detected included RSV-B (43.3%), BKV (23.3%), more than one virus (10%), cytomegalovirus (CMV) (6.7%), RSV-A (6.7%), HSV (3.3%), HHV-6 (3.3%), and CVB3 (3.3%). Alterations of consciousness and seizures were the most frequently presented symptoms. Neuroimaging detected abnormalities in 19 (76%) patients. The cerebral spinal fluid cell count, protein, and glucose concentration were elevated in eight (26.7%), 18(60%), and nine (30%) patients, respectively. The treatment efficacy and prognoses varied considerably based on the different causative viruses. Multivariate analyses revealed that acute graft-versus-host disease (grade III-IV), CMV viremia, and engraftment syndrome were significantly and independently associated with VE. The cumulative mortality rate was significantly higher in patients suffering from VE than in the controls.Characteristics, such as onset time, response to treatment, and outcome, varied based on the different causative viruses.