Allogeneic hematopoietic stem cell transplantation for transfusion-dependent pyruvate kinase deficiency in Chinese children: A multicenter retrospective study

Abstract Background Pyruvate kinase deficiency (PKD) is a rare hereditary hemolytic anemia caused by PKLR gene mutations that disrupt erythrocyte energy metabolism. Current therapeutic approaches for PKD include splenectomy, enzyme replacement therapy, and allogeneic hematopoietic stem cell transplantation (allo-HSCT). For transfusion-dependent patients where splenectomy benefits only a subset and enzyme replacement therapy is unavailable in China, allo-HSCT offers an effective curative approach. This study aimed to evaluate the efficacy and safety of allo-HSCT in Chinese pediatric patients with transfusion-dependent PKD. Methods This multicenter retrospective analysis included 35 transfusion-dependent PKD children undergoing allo-HSCT across 13 Chinese hospitals between February 2009 and December 2023. Demographic characteristics, genetic profiles, transplant protocols, and clinical outcomes were analyzed. Graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS) was defined as a composite end point of death from any cause, graft failure (primary/secondary), grade 3 to 4 acute GVHD, or chronic GVHD requiring systemic immunosuppression therapy. Overall Survival (OS) and GRFS were estimated using the Kaplan–Meier methodology. Cumulative incidences of acute GVHD and chronic GVHD were analyzed separately in competing risk models. Results The cohort (25 males, 10 females) had a median diagnosis age of 4 months (range,1 month-7 years 7 months) and transplant age of 2 years 3 months (range,6 months-9 years 2 months). All patients harbored PKLR gene mutations (14 non-missense mutations, 40%). Three patients underwent splenectomy pre-HSCT, and 11 received iron chelation therapy pre-HSCT. Median pre-transplant serum ferritin was 940 ng/ml (range,268–3483 ng/ml) and total bilirubin was 44.5 μmol/L (range,5.3–119.3μmol/L). Donor types included: matched sibling donors (8, 22.9%), matched unrelated donors (12, 34.3%), haploidentical donors (5, 14.3%), and mismatched unrelated donors (10, 28.6%). Stem cell sources comprised peripheral blood (21, 60%), peripheral blood plus bone marrow (7, 20%), and umbilical cord blood (7, 20%). Median CD34 positive cell doses were 8.3 × 106/kg (range,2.9-23.0×106/kg) in peripheral blood / bone marrow groups and 3.6 × 105/kg (range,1.8-6.8×105/kg) in umbilical cord blood group. Busulfan-based myeloablative conditioning was administered in 34 patients (97.1%). GVHD prophylaxis consisted of: anti-thymocyte globulin (ATG) with calcineurin inhibitors (CNI, 27, 77.1%), ATG plus post-transplant cyclophosphamide with CNI (7, 20.0%), and CNI alone (1, 2.9%). All patients achieved engraftment. Median time to neutrophil recovery was 13 days (range, 11-22 days), platelet recovery 19 days (range, 8-48 days), and red blood cell recovery 17 days (range, 7-47 days). Secondary mixed chimerism occurred in 3 patients: 2 converted to full donor chimerism after donor lymphocyte infusion (1) or immunosuppression tapering (1); 1 maintained stable mixed chimerism (≈90%) with normal blood counts without intervention. Seven patients developed grade 2 acute GVHD, four grade 3–4 acute GVHD, seven mild chronic GVHD, and one moderate chronic GVHD. The 100-day cumulative incidences of grade 2–4 acute GVHD and grade 3–4 acute GVHD were 31.4% (95% confidence interval [CI], 15.8–47.1%) and 11.4% (95% CI, 7.3–22.1%), respectively. The 1-year cumulative incidence of chronic GVHD was 22.9% (95% CI, 8.7–37.0%). All GVHD cases resolved with immunosuppression discontinuation. Hepatic veno-occlusive disease (VOD) occurred in 5 patients (4 resolved, 1 fatal). Among the 35 patients, one child died of VOD on day 67 post-transplant. The remaining 34 children remained disease-free. With a median follow-up of 44 months (range, 67 days to 15 years), 5-year OS and GRFS were 97.1% (95% CI 91.8-100.0%) and 85.7% (95% CI 74.9-98.1%), respectively. Conclusion Allo-HSCT demonstrates high efficacy and acceptable safety for transfusion-dependent PKD in Chinese children, achieving 97.1% OS and 85.7% GRFS. Despite complications including GVHD and VOD, proactive intervention ensured favorable outcomes. Where enzyme replacement therapy is inaccessible or ineffective, or when patients decline splenectomy or are unresponsive to it, allo-HSCT provides a definitive therapeutic strategy. These findings support consideration for its integration into severe PKD treatment algorithms.