CD40LG and immune system disorder: However, the authors indicated that FA was more commonly reported in patients with specific PIDs, compared to what would be expected in the general population, i.e., in the presence of combined immunodeficiencies (33.3%), sIgAD (25%), CD40 ligand deficiency (7.7%), primary hypogammaglobulinemia (7.1%), hyper IgE syndrome (6.3%) [11].