Genetic analysis of IgG4-related disease.

IgG4-related disease (IgG4-RD) is an emerging concept of a novel clinical entity, characterized by the swelling of the affected organs, increase in serum total IgG and IgG4 levels, infiltration of plasmacyte and eosinophil, fibrosis of the affected lesions and good response to corticosteroid. IgG4-RD includes diseases with organ-specific fibrosis and infiltration of IgG4-positive plasmacyte, previously known as type 1 autoimmune pancreatitis (AIP), Mikulicz's disease and others. Although the precise mechanisms of the pathogenesis of IgG4-RD are not yet understood, some studies have suggested genetic components contributing to the onset of IgG4-RD or its subgroup. The recent emergence of the concept of IgG4-RD has made it difficult to conduct genetic analyses of IgG4-RD as a whole. When the analyses are restricted to the various subgroups of IgG4-RD, they require a large number of DNA samples from patients satisfying IgG4-RD diagnostic criteria not completely overlapping the criteria in type 1 AIP, Mikulicz's disease and others. Not only HLA but also non-HLA genes have been described as IgG4-RD risk genes, particularly in type 1 AIP. In this mini-review article, we will explore previous studies analyzing genetic associations with IgG4-RD and its subgroups, and discuss the future direction of the research addressing the existing problems.