was the first to report deceased circulating levels of HDL cholesterol and Apolipoprotein A-I (ApoA-I), the major protein component in HDL, in a combined cohort of patients with CVID (n=18) and X-linked agammaglobulinemia (XLA, n=6), compared to healthy controls (38). Here, APOA1 is linked to isolated agammaglobulinemia.