Previous case reports describing P. aeruginosa sepsis in children with known PIDs, such as Wiskott–Aldrich syndrome, X-linked agammaglobulinemia, cyclic neutropenia, and IRAK-4/MyD-88 deficiency (8, 10, 22, 34), were based on conventional, candidate–gene-driven immunological testing. Here, IRAK4 is linked to X-linked agammaglobulinemia.