Abstract
A 68-year-old man was admitted because of a pulsatile mass and pain in the left temporal region, and computed tomography demonstrated the superficial temporal artery aneurysm. He underwent aneurysmectomy, and pathologic investigation revealed marked thickness of the adventitia with substantial plasmacyte infiltration. On immunoglobulin G4 (IgG4) immunohistochemistry, IgG4-positive lymphocytes were scattered in the adventitia, and biochemical tests revealed elevation of IgG4 (200 mg/dL). The case satisfied the criteria for both giant cell arteritis and IgG4-related disease (IgG4-RD). This case report suggested that IgG4-RD can occur in the superficial temporal artery and that IgG4-RD may partially overlap with a subtype of giant cell arteritis.