Clinical Characteristics and Outcome of BK Virus Infection in Pediatric Patients with Hematopoietic Stem Cell Transplant
Miguel Mayorga Vargas, Martha Avilés Robles, Israel ParraAbstract
Background
Primary BK virus (BKV) infection typically occurs in early childhood without significant clinical sequelae. Epidemiological studies have shown that 70% of children are infected with BKV by the age of 10 years. Following primary infection, BKV remains latent and does not cause notable morbidity in immunocompetent individuals. However, in immunosuppressed individuals, such as transplant recipients, clinically significant reactivation of latent BKV may occur. In hematopoietic stem cell transplant (HSCT) recipients, the most frequent manifestation associated with BKV reactivation is hemorrhagic cystitis (HC). The overall incidence of BKV infection in HSCT patients has been reported to exceed 80%, with 30% of these cases progressing to HC. Among HC cases, symptoms typically manifest at a median of 35 days post-transplant, and this is closely associated with the type of conditioning regimen used.
Methods
This was an observational, retrospective case series study including pediatric patients who underwent HSCT and had BKV infection, with follow-up conducted between January 2019 and December 2023. Statistical analysis involved the description of demographic characteristics, clinical manifestations, viremia/viruria levels, and outcomes following BKV reactivation. Additionally, variable cross-analysis was performed to identify risk factors associated with clinical outcomes in the study population.
Results
Twenty-nine patients were identified with positive BKV viral loads, 55% of whom were male, with a median age of 10 years. Seventy-two percent of the patients underwent HSCT due to an underlying malignancy. Allogeneic HSCT was the most common type, accounting for 93% of cases, and peripheral blood was the source of hematopoietic stem cells in 79%. Regarding conditioning regimens, 69% received a chemotherapy-based myeloablative protocol. Of the cases with BKV-associated viruria and viremia, 10% developed hematuria and 3% progressed to hemorrhagic cystitis; all these cases had received myeloablative conditioning. Patients with hemorrhagic manifestations exhibited viruria exceeding 4 × 106 copies/mL and concurrent viremia ranging from 933 to 25,361 copies/mL. Hemorrhagic symptoms appeared, on average, 89.3 days post-transplant.
Conclusions
In our study, BK virus-associated hemorrhagic cystitis was an infrequent complication in pediatric HSCT recipients. The use of a myeloablative conditioning regimen was identified as a risk factor not only for the development of BKV-associated hemorrhagic cystitis but also for the presence of BKV viremia and viruria.