*3.2. Immunological Evaluation*

The four CVID patients had undetectable or very low IgM and IgA levels from diagnosis. After IVIG treatment, all patients reached a normal IgG level, which is currently maintained. The analysis of lymphocyte subsets showed CD4+ T cell lymphopenia in Cases 3 and 4, a remarkable reduction of NK cells in Cases 1 and 4, and a very low B cell count in Case 1. B cell immunophenotype highlighted the reduction in switched memory B cells in all cases except in Case 3, in which they were absent. CD21*low* B cells were increased in Case 1 and transitional B cells were remarkably increased in Case 3. EURO-Class classification group and immunological data are indicated in Table 1.
