BTK and isolated agammaglobulinemia: Predominately antibody deficiencies are another IUIS phenotypic category of interest where we identified 5 IEI genes associated with type 2 inflammation (NFKB2, BTK, PIK3CD, PIK3R1, TNFRSF13B). X-linked agammaglobulinemia (XLA) caused by pathogenic BTK variants typically presents clinically around 4 to 6 months of age when the IgG antibodies transferred through the placenta begin to diminish (50).