TNFRSF13B and X-linked lymphoproliferative disease: Finally, the patient underwent DNA sequencing and analysis to screen for genetic mutations that have been linked to primary immune deficiencies, including those associated with hyper-IgM syndrome (UNG, AICDA, CD40, and CD40LG), CVID (TNFRSF13B (TACI)), X-linked lymphoproliferative disease (XIAP), and autoimmune lymphoproliferative syndrome (ALPS) (CASP8, CASP10, FADD, FAS, FASLG, KRAS, MAGT1, and NRAS).