To define the expanded population of DN T cells in inherited CD4 deficiency, we immunophenotyped these cells using a flow cytometric panel adapted from a recent study that characterized conventional DN (CD38−CD45+/−) versus pathogenic DN (CD38+CD45+) T cells in FAS-deficient patients (Maccari et al., 2021). This evidence concerns the gene CD38 and immunodeficiency 79.