Acute kidney injury during ruxolitinib therapy in pediatric patients with graft-versus-host disease: incidence, associated factors, and histopathological findings in a retrospective cohort study.

Ruxolitinib is a cornerstone treatment for steroid-refractory graft-versus-host disease (GVHD) following allogeneic hematopoietic stem cell transplantation (HSCT) in children, yet longitudinal data on kidney function during such therapy remain limited. We retrospectively analyzed 38 pediatric patients (0-18 years) receiving ruxolitinib for acute or chronic GVHD between January 2018 and December 2025, assessing kidney function at six timepoints from baseline to month 6. Mean serum creatinine rose from 0.34 ± 0.16 mg/dL at baseline to 0.50 ± 0.34 mg/dL at month 3 (p < 0.001) and remained mildly elevated at month 6 (0.48 ± 0.23 mg/dL; p < 0.001). Acute kidney injury (AKI) occurred in 7 patients (18.4%) at a median of 2.36 months after ruxolitinib initiation, with 4 (57.1%) progressing to acute kidney disease; biopsies excluded BK virus nephropathy. BK virus reactivation, BKV-related hemorrhagic cystitis, CMV reactivation, older age at transplantation, and higher baseline creatinine were significantly associated with AKI, whereas ruxolitinib dose was not. Post-transplant AKI in this setting appears multifactorial; controlled studies including a ruxolitinib-unexposed comparator group are needed to clarify the specific contribution of the drug.