Inborn Errors of Immunity and Hematopoietic Cell Transplantation: Recognition and Pretransplant Management.

Primary immunodeficiencies, now more broadly termed as "inborn errors of immunity (IEI)," are rare genetic disorders associated with recurrent infections, immune dysregulation, autoimmunity, lymphoproliferation, and malignancy risk. Early recognition and diagnosis are essential to reduce infection-related morbidity, prevent organ damage, and identify children who may benefit from curative therapy. A comprehensive history, physical examination, targeted immune evaluation, and genetic testing can support diagnosis, while early supportive measures may reduce infection risk before definitive therapy. Treatment may include antimicrobial prophylaxis, immunoglobulin replacement, enzyme replacement, immune-modifying agents, gene-based therapies, and allogeneic hematopoietic cell transplantation (HCT), which can be curative for select IEI. However, HCT requires careful pretransplant evaluation, as outcomes are influenced by disease biology, infection burden, organ function, donor availability, graft-versus-host disease risk, and conditioning toxicity. This review focuses on recognition of IEI, initial evaluation, supportive care, and pre-HCT management for pediatricians.