Whole exome sequencing approach has proved to be instrumental in identifying mutations in capillary sequencing negative cases of X-linked agammaglobulinemia (XLA) [149], severe combined immunodeficiency (SCID) [148], B cell expansion with NF-κB, and T cell anergy (BENTA) [176], apart from targeted next generation sequencing in SCID [177] and major histocompatibility complex class II deficiency [178]. The gene discussed is NFKB1; the disease is severe combined immunodeficiency.