Pericardial effusion as a potential site of localized DNA virus reactivation following U-CB transplantation

Pericardial effusion (PCE) is a serious complication after allogeneic hematopoietic cell transplantation, but its etiology is not fully understood, particularly the role of viral reactivation. We investigated the presence of DNA viruses in pericardial fluid from nine umbilical cord blood transplant recipients who underwent pericardiocentesis. Multiplex PCR detected DNA viruses in seven patients (78%), with Epstein–Barr virus being most common. The clinical context of viral detection appeared to differ by onset timing. In early-onset PCE (< 100 days), viral presence was often systemic and likely secondary to severe inflammation. In contrast, late-onset cases frequently occurred with chronic graft-versus-host disease and showed localized viral reactivation within the pericardium. These findings suggest DNA viruses are potential contributors to post-transplant PCE. Viral evaluation of pericardial fluid should be considered in these patients as it may influence therapeutic strategies.