While each of the patients with inherited CD4 deficiency displayed an infectious phenotype, it was, however, milder than that reported for people with CD4+ T cell deficiency due to HIV infection, HLA class II deficiency, or idiopathic CD4+ T cell lymphopenia (Al-Herz et al., 2013; Ben-Mustapha et al., 2013; Gottlieb et al., 1981; Lisco et al., 2023; Masur et al., 1981; Ouederni et al., 2011; Rozmus et al., 2013; Small et al., 1983; Vieira et al., 1983). Here, CD4 is linked to congenital T-cell immunodeficiency.