Increased serum IgG4 levels and intimal IgG4-positive cell infiltration in rapidly growing aortic aneurysm.

A 67-year-old Japanese man had been complaining of discomfort in the chest and back and feeling febrile for 2 weeks. Chest computed tomography indicated a thoracic aortic aneurysm. He occasionally showed a high fever (up to 38.0°C), even after hospital admission, irrespective of antibiotic therapy. The patient was found to have elevated serum IgG4 levels (366 mg/dL). The aneurysm demonstrated rapid growth; therefore, rifampicin-soaked woven Dacron synthetic graft replacement was performed 22 days after admission. Immunohistostatining of the resected aorta segment showed an IgG4-positive plasma cell infiltrate within the intimal layer neighboring the cholesterol-rich atheromatous plaque. After surgery, the patient's serum IgG4 level dropped acutely; however, it did not reach the normal range. The possible role of IgG4 in the development or suppression of aortic remodeling, as well as in atherogenesis, among patients with rapidly growing aortic aneurysm requires further investigation.