Gain-of-function (GoF) mutations in the PIK3CD or PIK3R1 gene encoding p110δ or p85α, respectively, have been identified by us and others in PID patients with a disorder now known as PASLI Disease (PI3Kδ-Activating mutation causing Senescent T cells, Lymphadenopathy, and Immunodeficiency), or APDS for short. Here, PIK3CD is linked to immune system disorder.