HLA-C and agammaglobulinemia: Age at time of study enrollment was 21.1 ± 15.7 years (mean ± SD) for patients with CVID, 18.0 ± 8.5 years for patients with agammaglobulinemia, 7.9 ± 7.8 years for patients with MHC class II deficiency, and 3.8 ± 4.9 years for SCID patients.