Inflammatory Aortic Aneurysm: Possible Manifestation of IgG4-Related Sclerosing Disease
K Raparia, C Molina, G Quiroga, S Shen, D Weilbaecher, A Ayala, JY Ro. The Methodist Hospital, Houston, TX
Background: Inflammatory aortic aneurysms (IAA) are associated with autoimmune disease; however, the precise pathogenetic mechanism still remains unclear. In this study, we investigate the hypothesis that IgG4-related autoimmune reaction is involved in the formation of IAA, like various other idiopathic sclerosing lesions such as those involving the pancreas and retroperitoneum.
Design: We studied clinico-pathologic features of 23 patients with IAA and 11 cases of atherosclerotic aortic aneurysms (AAA) served as a control group. These cases were retrieved from the surgical pathology files of our hospital from 1995 to 2007. We evaluated the expression of IgG4 in both IAA study and control group. The number of IgG4 positive plasma cells was scored semi quantitatively per single 20X field as follows: 0 (no positive plasma cells), 1(≤20 cells), 2(21 to ≤50 cells), and 3(>50cells).
Results: Of the 23 patients, 20 were males and 3 were females (M: F ratio 6:1); age ranged from 43 to 81 years (average 64.3 years). Clinically, an abdominal mass was detected in 19 patients and abdominal pain was present in 4 patients at presentation. Histologically, all 23 cases of IAA formed a mass that displayed inflammatory myofibroblastic tumor-like features. Immunohistochemically, the number of infiltrating IgG4-positive plasma cells in IAA cases exceed that of AAA cases. Score of 0 was seen in 2/23 of IAA and 3/11 of AAA patients; score of 1 was seen in 7/23 of IAA and 5/11 of AAA patients; score of 2 was seen in 1/23 of IAA and 3/11 of AAA and score of 3 was seen in 13/23 of IAA and 0/11 of AAA patients. Thus, 57% of IAA cases showed score 3 of IgG4-positive plasma cells, whereas none of the 11 cases of AAA showed score 3 IgG4-positive plasma cells (P=0.0018, Fischer's exact test).
Conclusions: Our findings suggest that IAA may be an aortic manifestation of the IgG4-related sclerosing disease, and not a simple inflammatory aneurysm. The high number of positive plasma cells, >50 plasma cells/one 20X field is more specific for the IAA than for AAA; however, lesser number can be seen in both IAA and AAA patients.
Monday, March 22, 2010 11:45 AM
Platform Session: Section G 2, Monday Morning