A number of previous studies have outlined the clinical phenotypes of large patient groups with antibody deficiency who have mutations in selected genes, including the TACI gene (Salzer et al., 2005; Zhang et al., 2007; Salzer et al., 2009), CTLA4 (Schwab et al., 2018), NFKB1 (Lorenzini et al., 2020), NFKB2 (Klemann et al., 2019), STAT3 (Fabre et al., 2019), PI3KCD (Jamee et al., 2020), or LRBA (Habibi et al., 2019). The gene discussed is CTLA4; the disease is agammaglobulinemia.