Objective: IgG4-related systemic disease, a disorder recognized only recently, can cause lymphoplasmacytic inflammation in the thoracic aorta. The percentage of cases caused by IgG4-related systemic disease is not known. We aimed to determine the percentage of noninfectious thoracic aortitis cases that are associated with IgG4-related systemic disease and to establish pathologic criteria for identifying involvement of the thoracic aorta by this disorder.
Methods: We searched our Pathology Service database to identify patients with noninfectious thoracic aortitis who underwent resection over a 5-year time span. The histologic features of these cases were reviewed. All cases of lymphoplasmacytic aortitis and representative cases of giant cell aortitis and atherosclerosis were stained by immunohistochemistry for IgG4 and for the plasma cell marker CD138. We determined the fraction of plasma cells that stained for IgG4.
Results: Of 638 resected thoracic aortas, 33 (5.2%) contained noninfectious aortitis. Four of these cases (12% of all patients with noninfectious aortitis) had histologic features of lymphoplasmacytic aortitis. Three of those 4 cases (9% of the noninfectious aortitis cases) demonstrated pathologic involvement by IgG4-related systemic disease, with an elevated proportion of plasma cells staining for IgG4 (mean +/- SD 0.82 +/- 0.08) compared with cases of giant cell aortitis (0.18 +/- 0.13) and atherosclerosis (0.19 +/- 0.08; P < 0.00001).
Conclusion: IgG4-related systemic disease accounted for 75% of lymphoplasmacytic aortitis cases and 9% of all cases of noninfectious thoracic aortitis in our institution during a 5-year period. Immunohistochemical assessment of the percentage of plasma cells that stained for IgG4 in resected aortas was helpful in identifying patients with IgG4-related systemic disease.