Stem cell transplantation for primary immune deficiency.

PURPOSE OF REVIEW: In this article, we summarize the recent advances in treating primary immune deficiency (PID) disorders by stem cell transplantation (SCT); we have focused on articles published in the past 2 years since the last major review of SCT for PID. RECENT FINDINGS: Analyses of the outcomes of SCT for PID by specific molecular defect have clarified which conditions are receptive to unconditioned transplants and which require more myeloablative conditioning. Improved outcomes for 'difficult' conditions [adenosine deaminase-severe combined immunodeficiency (ADA-SCID), major histocompatibility complex class II deficiency] and potential advantages of using cord blood as a stem cell source have also been described. Newborn screening for SCID identifies well babies with SCID: the optimal SCT protocol for such young infants remains to be determined. Reduced toxicity conditioning has been successfully used to treat conditions such as Wiskott-Aldrich syndrome and chronic granulomatous disease, offering curative engraftment with reduced transplant-related mortality. Similarly, treating children with familial hemophagocytic lymphohistiocytosis using reduced intensity conditioning SCT results in much improved outcomes. Advances in next generation sequencing have identified new diseases amenable to SCT, such as DOCK8 deficiency, resulting in improved quality of life and protection from malignancy. SUMMARY: Recent studies suggest that further improvements in treating PID with SCT are possible with a greater understanding of the genetics and immunobiology of these diseases, facilitating the matching of donor type and conditioning regimens, or indeed alternative therapies (such as gene therapy) to specific PID disorders.