In a PCA using the robust features, the controls separated well from CVID patients, as well as CVID-like disorders caused by specific IEI, such as deficiencies in KMT2D (Kabuki syndrome), ICOS (Inducible T cell costimulator), AICDA (encoding AID), NFκB2 (nuclear factor kappa B subunit 2), and APDS2 (Activated PI3K-delta Syndrome Type 2) caused by loss-of-function mutations in the regulatory subunit of PI3K (PIK3R1) (Fig. 4d). Here, ICOS is linked to common variable immunodeficiency.