In this study, we evaluated the clinical utility of TGP sequencing and its impact on both prognosis and different therapeutic approaches in a subset of patients with unclassified antibody deficiency and for whom a monogenic form was suspected based on the presence of syndromic features along with severe hypogammaglobulinemia or signs of immune dysregulation in the form of autoimmunity or inflammatory disease. This evidence concerns the gene TGM4 and agammaglobulinemia.