A new clinicopathological entity of IgG4-related inflammatory abdominal aortic aneurysm

ObjectiveRecently, the relationship between immunoglobulin (Ig)G4 and idiopathic sclerosing lesions has attracted much attention. IgG4-related disease was first described with regard to the pancreas (autoimmune pancreatitis), and has been expanded to various organ systems. We previously reported that inflammatory abdominal aortic aneurysm (IAAA) could be one of the manifestations of IgG4-related disease. In this study, we tried to elucidate the clinical characteristics of IgG4-related IAAA.MethodsThis study consisted of 23 cases of IAAA and 40 cases of atherosclerotic abdominal aortic aneurysm (AAA). Clinical presentation, laboratory findings, and pathological features were examined. Aneurysms of 13 cases histologically corresponded to IgG4-related IAAA.ResultsThose cases accounted for 5% of all surgical AAAs, and 57% of IAAAs. Compared to non-IgG4-related IAAA, IgG4-related cases were characterized by less frequent association with abdominal or back pain. Serum IgG4 concentrations were significantly elevated in IgG4-related cases. Interestingly, patients with IgG4-related IAAA frequently showed an allergic constitution, such as drug allergy, autoimmune diseases, high serum IgE concentrations, and a high titer of antinuclear antibody. Pathologically, IgG4-related cases were characterized by more significant thickening of the adventitia and more numerous IgG4-positive plasma cell infiltrations. Three non-IgG4-related cases showed aneurysmal rupture at the time of first presentation, whereas no IgG4-related cases showed rupture.ConclusionRecognizing a new disease entity of IgG4-related IAAA seems important because this was clinically and pathologically different from conventional aAAA and non-IgG4-related IAAA.Clinical RelevanceIgG4-related disease was determined by irregular fibrous tissue proliferation with numerous infiltrations of IgG4-positive plasma cells and concentration of serum IgG4, and clinically characterized steroid sensitivity. We examined 23 cases of IAAA and 40 cases of aAAA, and revealed about half cases of IAAA was linked to the peri-aortic counterpart of IgG4-related disease. IgG4-related IAAA was clinicopathologically different from conventional aAAA and non IgG4-related IAAA, that is, IgG4-related IAAA was particularly characterized by frequency of complication of autoimmune diseases, low incidence of rupture, and high serum IgE concentration