HLA-mismatched transplants with either in vitro depletion of CD3+TCRαβ/CD19 (TCRαβ) cells or in vivo T-cell depletion using post-transplant cyclophosphamide (PTCY) have been increasingly used for patients with inborn errors of immunity (IEI). We performed a retrospective multicenter study via the EBMT registry on 306 children with IEI undergoing first transplant between 2010-2019 from an HLA-mismatched donor using TCRαβ (n=167) or PTCY (n=139). Median age at HSCT was 1.2 years (range, …