Pathogenic homozygous variants in the ITK gene can give way to a wide spectrum of different phenotypic expressions, including isolated hypogammaglobulinemia and varying degrees of T-cell loss with low counts of naive CD4+ cells and NKT cells, susceptibility to recurrent infections, autoimmune phenomena, autoimmune lymphoproliferative syndrome with an increased risk of EBV-related Hodgkin and non-Hodgkin lymphoma, hemophagocytic lymphohistiocytosis (HLH), and atypical epidermodysplasia verruciformis with a predisposition to human papilloma virus (HPV) skin infection [12,13,14,15]. Here, CD4 is linked to autoimmune lymphoproliferative syndrome.