Therefore, the simple measurement of serum immunoglobulins (IgA, IgG, IgM and IgE) was recommended, in addition to the sweat test for cystic fibrosis: as reported in Table 2, hypogammaglobulinemia with severe reduction of IgG and total IgA deficiency (without hyper-IgM and hyper-IgE findings) was evidenced, which was consistent with a diagnosis of CVID. Here, CD40LG is linked to cystic fibrosis.