Autoimmune diseases associated with common variable immune deficiency.

Common variable immunodeficiency (CVID) is the most prevalent primary immune deficiency, affecting roughly 2-4/100 000 individuals in the general population. The etiology is currently unknown, even if several genetic mutations have been described, and no single clinical feature or single laboratory test can establish the diagnosis, which is based on multiple criteria. CVID is characterized by B- and T-cell dysfunction that predisposes to an increased risk of infections, with the typical involvement of the respiratory and gastrointestinal tracts. Besides this well-established complication, though the coexistence of immunodeficiency and autoimmunity appears paradoxical, two-thirds of CVID patients present concomitant autoimmune disorders. Of note, autoimmunity can often be the only clinical manifestation of CVID at the time of diagnosis. The most common autoimmune disorders associated with CVID are autoimmune cytopenias, that is, immune thrombocytopenic purpura and autoimmune hemolytic anemia, either as separate entities or as concurrently (Evans syndrome). CVID patients can also manifest rheumatologic diseases (eg, arthritis, Sjogren's disease, systemic lupus erythematosus, vasculitis, Behçet's syndrome) and gastrointestinal autoimmune disorders (eg, ulcerative colitis, autoimmune atrophic gastritis, celiac disease). This latter may pose a particular diagnostic challenge, as celiac-specific autoantibodies can be absent in CVID patients. Understanding the molecular basis and the clinical impact of autoimmunity in CVID patients might help manage CVID, thus reducing its diagnostic delay and preventing its complications.