In this regard, we have leveraged the recent finding of an hypomorphic variant on the interleukin 2 receptor subunit γ or common γ chain (IL2RG) gene in a patient with antibody deficiency and CD4 lymphopenia followed in our clinic for more than three decades to explore the functional alteration by several non-routine assays. This evidence concerns the gene IL2RG and agammaglobulinemia.