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The Primary Immune Deficiency Treatment Consortium (PIDTC) is enrolling children with severe combined immunodeficiency (SCID) to a prospective natural history study. We analyzed patients treatedwith allogeneic hematopoietic cell transplantation (HCT) from 2010 to 2014, including 68 patientswith typical SCID and 32 with leaky SCID, Omenn syndrome, or reticular dysgenesis. Most (59%) patients were diagnosed by newborn screening or family history. The 2-year overall survivalwas 90%, but was 95%for thosewhowere infection-free at HCTvs 81%for those withactive infection (P5.009). Other factors, including thediagnosis of typical vs leaky SCID/Omenn syndrome, diagnosis via family history or newborn screening, useofpreparative chemotherapy, or thetypeof donorused, did not impact survival. Although 1-year post-HCT median CD4 counts and freedom from IV immunoglobulin were improved after the use of preparative chemotherapy, other immunologic reconstitution parameters were not affected, and the potential for late sequelae in extremely young infants requires additional evaluation. After a T-cell-replete graft, landmark analysis at day 1100 post-HCT revealed that CD3 < 300 cells/μL, CD8 < 50 cells/μL, CD45RA < 10%, or a restricted Vb T-cell receptor repertoire (<13 of 24 families) were associated with the need for a second HCT or death. In the modern era, active infection continues to pose the greatest threat to survival for SCID patients. Although newborn screening has been effective in diagnosing SCID patients early in life, there is an urgent need to identify validated approaches through prospective trials to ensure that patients proceed to HCT infection free. [ABSTRACT FROM AUTHOR]

The safety and efficacy of reduced-intensity conditioning (RIC) regimens for the treatment of pediatric acute myeloid leukemia is unknown. We compared the outcome of allogeneic hematopoietic cell transplantation in children with acute myeloid leukemia using RIC regimens with those receiving myeloablative-conditioning (MAC) regimens. A total of 180 patients were evaluated (39 with RIC and 141 with MAC regimens). Results of univariate and multivariate analysis showed no significant differences in the rates of acute and chronic graft-versus-host disease, leukemia-free, and overall survival between treatment groups. The 5-year probabilities of overall survival with RIC and MAC regimens were 45% and 48%, respectively (P = .99). Moreover, relapse rates were not higher with RIC compared with MAC regimens (39% vs 39%; P = .95), and recipients of MAC regimens were not at higher risk for transplant-related mortality compared with recipients of RIC regimens (16% vs 16%; P = .73). After carefully controlled analyses, we found that in this relatively modest study population, the data supported a role for RIC regimens for acute myeloid leukemia in children undergoing allogeneic hematopoietic cell transplantation. The data also provided justification for designing a carefully controlled randomized clinical trial that examines the efficacy of regimen intensity in this population. [ABSTRACT FROM AUTHOR]