Purpose of review: To summarize recent publications on clinical and genetic aspects of IgA deficiency (IgAD).
Recent findings: Both major histocompatibility complex (MHC) and non-MHC genes contribute to susceptibility to the disease. The former genes appear to be located in different parts of the MHC region depending on the HLA haplotype. The latter show a marked overlap with genes associated with a variety of autoimmune disorders including Graves' disease, systemic lupus erythematosus, type 1 diabetes and celiac disease, suggesting common pathophysiological mechanisms. Various cytokines, recently shown to include interleukin 21, can induce IgA synthesis in vitro in cells from patients with IgAD, suggesting a regulatory basis of the disease.
Summary: IgAD is the most common primary immunodeficiency in the Western world with a prevalence of approximately 1 : 600 in the general population. It appears to be a polygenic disorder and several of the genes involved have recently been identified. The involvement of genes associated with autoimmunity may suggest that IgAD in itself is an autoimmune disease.