Hypogammaglobulinemia typically involves all classes of immunoglobulins (IgG, IgA, IgM), but mostly the IgM class (in 56.7% of patients) as well as IgG3 (52%) and IgG1 (28%) subclasses [11], [12]. The gene discussed is CD40LG; the disease is Decreased circulating immunoglobulin concentration.