The Power of Hematopoietic Stem Cell Transplantation (HSCT): A Curative Approach for Diffuse Large B‐Cell Lymphoma (DLBCL) Incidentally Detected in a SCID Baby

ABSTRACT Lymphoma is a rare complication of X‐linked severe combined immunodeficiency (X‐SCID) caused by IL2RG deficiency. We report an infant with IL2RG ‐SCID who developed diffuse large B‐cell lymphoma (DLBCL) during pretransplant evaluation. A male infant with T−B+ SCID was diagnosed at 1 month of age and referred for hematopoietic stem cell transplantation (HSCT). Pretransplant imaging unexpectedly revealed a thoracic mass, and biopsy confirmed EBV‐negative DLBCL. Rituximab and low‐dose chemotherapy failed to reduce the mass and were complicated by severe infections. The patient subsequently underwent unconditioned haploidentical HSCT with posttransplant cyclophosphamide. Full donor T‐cell chimerism was achieved by Month 3, and complete resolution of the lymphoma was observed 15 months after HSCT. Successful HSCT and immune reconstitution may achieve lymphoma control in IL2RG ‐SCID when conventional chemotherapy is poorly tolerated. Trial Registration : The authors have confirmed clinical trial registration is not needed for this submission.