Predictors of the progression of immunoglobulin-G4-related abdominal aortic aneurysms after endovascular therapy

Objective : Approximately half of inflammatory abdominal aortic aneurysms, defined by the prominent thickening adventitia, are immunoglobulin G4 (IgG4)- related diseases characterized by elevated serum IgG4 and IgG4-positive-plasmacytes infiltration. IgG4-related AAAs (IgG4-AAAs) exhibit vasculitis with elevated inflammatory marker levels. Matrix metalloproteinases (MMPs) degrade the extracellular matrix to destroy the aortic structures to progress aneurysm. This report examined pre- and postoperative serum MMPs and inflammatory marker levels to evaluate the prognosis of IgG4-AAAs after endovascular aortic repair (EVAR). Methods : Among 25 patient with inflammatory abdominal aortic aneurysms (>2-mm-thick periaortic fibrosis) treated with EVAR, IgG4-AAA was diagnosed in 14 patients, and the remaining 11 patients were classified as non-IgG4-AAA. IgG4-AAAs were categorized into cases with increased (IgG4-AAA-up; n = 6) or decreased (IgG4-AAA-down; n=8) postoperative serum IgG4 levels. Before EVAR and after 24 months, we compared the serum MMP, inflammatory marker levels, periaortic fibrosis, and aneurysm diameter. Results : IgG4-AAAs patients showed higher preoperative IL-6 levels, increased postoperative MMP-9 levels, and enlarged postoperative aneurysmal diameters compared with non-IgG4-AAA patients. Among IgG4-AAAs, IgG4-AAA-up exhibited higher preoperative MMP-9, higher preoperative monocytes and eosinophils, increased postoperative MMP-9 and IL-6, and larger aneurysm diameter than IgG4-AAA-down. All patients in IgG4-AAA-down showed shrunk preoperative aneurysm, although almost all patients in IgG4-AAA-up showed enlarged. In IgG4-AAA-up, IgG4/IgG ratio was significantly higher consistently before and after EVAR. MMP-9 was significantly correlated with IgG4 and IL-6. MMP-2 was not significantly different between patients with and without as well as between IgG4-AAA-up and IgG4-AAA-down. Conclusion: Increased postoperative MMP-9 and IL-6 in IgG4-AAA may accelerate aneurysmal progression after EVAR. IgG4-AAA-up exhibited increased IL-6 levels and larger aneurysm diameters following EVAR than IgG4-AAA-down and were considered as the high-risk group with a tendency toward progression. Before surgery, a high IgG4/IgG ratio, high MMP-9 concentrations, a high ratio of monocytes and eosinophils might predict IgG4-AAA-up.