Besides, alterations in the gut microbiota composition have been described in patients with SIgAD [56]; however, it is difficult to establish whether it contributes to the development of immunoglobulin deficiency, or rather it is a result of impaired function of the mucosal barrier in a condition of the paucity of secretory IgA. This evidence concerns the gene CD79A and Decreased circulating immunoglobulin concentration.