Original ArticlesInflammatory Abdominal Aortic Aneurysm: Close Relationship to IgG4-related PeriaortitisKasashima, Satomi MD, PhD* †; Zen, Yoh MD, PhD*; Kawashima, Atsuhiro MD, PhD†; Konishi, Keiko MD, PhD‡; Sasaki, Hisao MD, PhD§; Endo, Masamitsu MD, PhD§; Matsumoto, Yasushi MD, PhD§; Kawakami, Kengo MD, PhD§; Kasashima, Fuminori MD, PhD§; Moriya, Makio MD§; Kimura, Keiichi MD, PhD∥; Ohtake, Hiroshi MD, PhD∥; Nakanuma, Yasuni MD, PhD¶Author Information *Division of Pathology, Kanazawa University Hospital Departments of †Pathology ‡Clinical Laboratory §Cardiovascular Surgery, National Hospital Organization, Kanazawa Medical Center Departments of ∥General and Cardiothoracic Surgery ¶Human Pathology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan Reprints: Yoh Zen, MD, PhD, Division of Pathology, Kanazawa University Hospital, 13-1 Takaramachi, Kanazawa 920-8641, Japan (e-mail: firstname.lastname@example.org). The American Journal of Surgical Pathology: February 2008 - Volume 32 - Issue 2 - p 197-204 doi: 10.1097/PAS.0b013e3181342f0d Buy Metrics Abstract Inflammatory abdominal aortic aneurysm (AAA) is a member of a family of disorders referred to as “chronic periaortitis” together with retroperitoneal fibrosis. Retroperitoneal fibrosis is included in IgG4-related disease, which is characterized by numerous infiltrating IgG4-positive plasma cells and high serum IgG4 concentrations. However, the relationship between IgG4-related disease and inflammatory AAA has not been documented. In this study, we examined the clinicopathologic characteristics of inflammatory (10 cases) and atherosclerotic (22 cases) AAAs, based on the hypothesis that inflammatory AAA might be related to IgG4-related disease. Cases of inflammatory AAA could be classified into 2 groups based on immunostaining of IgG4. Four patients showed diffuse infiltration of abundant IgG4-positive plasma cells (IgG4-related cases), whereas the remaining 6 cases of inflammatory AAA and all cases of atherosclerotic AAA had only a few IgG4-positive plasma cells (non–IgG4-related cases). IgG4-related inflammatory AAA was pathologically characterized by the frequent infiltration of eosinophils, lymph follicle formation, perineural inflammatory extension, and inconspicuous infiltration of neutrophils compared with non–IgG4-related inflammatory AAA. Obliterative phlebitis, which is venous occlusion with inflammatory cell infiltration, is observed in all IgG4-related cases. In addition, serum IgG4 concentrations were significantly higher in IgG4-related inflammatory AAA (109 to 559 mg/dL, normal range: 4 to 110 mg/dL) than non–IgG4-related inflammatory AAA (32 to 59 mg/dL) and all atherosclerotic AAA (12 to 83 mg/dL). In conclusion, inflammatory AAAs might be classified into 2 groups: IgG4-related or nonrelated. The former might be one of the IgG4-related diseases, and could be included in IgG4-related periaortitis together with retroperitoneal fibrosis. © 2008 Lippincott Williams & Wilkins, Inc.