Severe hemorrhagic cystitis caused by the BK polyomavirus is associated with decreased survival post‐allogeneic hematopoietic stem cell transplantation

Background BK polyomavirus reactivation can occur following allogeneic hematopoietic stem cell transplantation (allo‐HSCT) and may lead to hemorrhagic cystitis (BKPyV‐HC). We hypothesized that development of BKPyV‐HC is associated with increased mortality post allo‐HSCT. Methods We retrospectively reviewed data on 133 adult patients (≥18 years old) who underwent allo‐HSCT from 2007 until 2014 at Hospital Israelita Albert Einstein in São Paulo, Brazil. Results Thirty‐six patients presented with BKPyV‐HC after a median time of 42 days, with a 1‐year cumulative incidence probability of 28.9% (95% CI 21.5%‐36.7%). In a multivariate Cox model, risk factors for development of BKPyV‐HC included younger age, male sex, development of grade 2‐4 acute graft‐versus‐host disease and recipients of umbilical cord blood grafts. Development of grade 3‐4 BKPyV‐HC (but not grade 1‐2) was associated with a decreased overall survival (OS) in a multivariate Cox model (hazard ratio [HR] 7.51, P