PIK3R1 and immunodeficiency disease: The genetic evaluation through WES achieved a definitive diagnosis in one case who showed an already described mutation in PIK3R1. Recently, heterozygous gain-of-function mutations in PIK3R1, encoding for p85α, one of the catalytic subunits of the PI3 kinase molecules, were reported as responsible for a novel form of immunodeficiency [28,29,30].