Clinical Picture of Post-Hematopoietic Cell Transplantation for Inborn Errors of Immunity: Single Center Experience

Background Long-term follow-up for inborn errors of immunity (IEIs) after hematopoietic cell transplantation (HCT) remains poorly described. We report ≥5 years post-HCT. Methods Retrospective data collection from 16 clinical records. Results 12 males (75%) and 4 females (25%) with diagnosis of IEIs (1 severe combined immunodeficiency [SCID], 6 CID, 4 phagocyte defect, 3 immune dysregulation disease, and 2 bone marrow failure). Median follow-up 5.3 years [0-14] and median age at transplant 6.5 years [0-17]. Patients received bone marrow (n = 15) or peripheral blood stem cells (n = 1), from matched family (n = 1), matched (n = 11), or mismatched (n = 4) unrelated donors using (10, 62.5%) busulfan–fludarabine, (2, 12.5%) busulfan–cyclophosphamide, (2, 12.5%) melphalan–fludarabine, and (1, 6.3%) fludarabine–cyclophosphamide conditioning. 93.8% received serotherapy (antithymoglobulin). Tacrolimus and methotrexate as graft versus host disease (GvHD) prophylaxis in 10 patients (62.5%). 8 patients (50%) developed acute and 3 (18.8%) chronic GVHD. 4 (25%) had CMV, 3 (18.8%) EBV, and 1 (6.3%) adenovirus viremia. 1 patient (6.3%) developed severe veno-oclusive disease and died on day +30, and 1 (6.3%) had secondary graft failure. Post-HCT analysis was made in the 14 remaining patients. 7 (50%) improved growth, 4 (28.6%) had significant infections, and 4 (28.6%) improved or stabilized lung disease. 5 (35.7%) developed autoimmunity, most (4, 80%) were hematological (neutropenia, thrombocytopenia, or hemolytic anemia). 11 (78.6%) required immunoglobulin replacement after HCT, 8 (57.1%) suspended it with a median of 698 days [423-4,397]. 8 (57.1%) achieved GvHD prophylaxis suspension at 488 days [360-723]. 12 patients had whole blood chimerism performed >50% [50-100]. At last follow-up, 14 patients were alive and with good chimerism, resulting in a 16-year overall survival of 93%. Conclusions HCT for IEIs resulted in high long-term survival in our cohort. Most patients achieved good chimerism and showed improvement in clinical outcomes, despite significant posttransplant complications (infections, autoimmunity, GvHD). These findings highlight the effectiveness of HCT while underscoring the need for long-term follow-up.