As it identifies the particular gain-of-function mutations in PIK3CD or PIK3R1 that define APDS, molecular diagnosis via genetic testing is the most dependable way of differentiation [10,12]. Functional experiments, including PI3Kδ overactivation research, can also show abnormal activation of the PI3K-AKT-mTOR pathway [13,46], further justifying the diagnosis. Understanding these differences is key to guaranteeing that patients receive the proper treatment since the therapy for APDS varies quite from that for other immunodeficiencies. Here, PIK3CD is linked to immune system disorder.