BACKGROUND:: METHODS:: RESULTS:: Fifty-five new, 14 updated, and 18 previously published patients were analyzed. Median age at HCT was 48 months (range, 1.5-552 months). Twenty-nine patients underwent transplantation for infection, 21 had malignancy, 13 had bone marrow failure, 13 received pre-emptive transplantation, 5 had multiple indications, and 6 had no information. Twenty-two received MAC, 59 received RIC, and 4 were infused; information was unavailable for 2 patients. Seventy-three of 77 patients with DNA ligase IV deficiency, Cernunnos-XLF deficiency, or Nijmegen breakage syndrome received conditioning. Survival was 53 (69%) of 77 and was worse for those receiving MAC than for those receiving RIC (P = .006). Most deaths occurred early after transplantation, suggesting poor tolerance of conditioning. Survival in patients with AT was 25%. Forty-one (49%) of 83 patients experienced acute GvHD, which was less frequent in those receiving RIC compared with those receiving MAC (26/56 [46%] vs 12/21 [57%], P = .45). Median follow-up was 35 months (range, 2-168 months). No secondary malignancies were reported during 15 years of follow-up. Growth and developmental delay remained after HCT; immune-mediated complications resolved. CONCLUSION