Is all inflammation within temporal artery biopsies temporal arteritis?

Temporal arteritis peaks during the eighth decade, affecting patients with frequent comorbidities who are especially prone to adverse effects of corticosteroid therapy. Perivascular inflammation involving small periadventitial vessels is not uncommon in otherwise normal temporal artery biopsies (TABs). As ischemic events occur in patients with non-temporal artery--based inflammation, it has been recommended that any vascular inflammation within TABs be treated with corticosteroids. We sought to determine whether such patients are at increased risk for temporal arteritis-like adverse events compared with age-matched controls devoid of inflammatory infiltrates. TABs without transmural temporal arteritic damage accessioned between 2002 and 2012 were reviewed for inflammation (>15 perivascular lymphocytes) involving small blood vessels and/or temporal artery adventitia. Of 343 TABs, 278 (81%) were negative for transmural arteritis. Inflammation involving small vessels and/or temporal artery adventitia was present in 56 cases (20%). Age-matched controls were available for 39 cases. With a mean follow-up of 5 years (range, 1-11 years), 6/39 (15%) of patients developed stroke or cardiovascular events or died compared with 7/39 (18%) of age-matched controls. None of the patients with study-positive TAB had documented steroid therapy before or after TAB. Our results demonstrate that patients with inflammation involving only small vessels or temporal artery adventitia are not at increased risk for temporal arteritis-like adverse events, and suggest that the risks of protracted corticosteroid therapy in this elderly population likely exceed any potential benefits. We advise against diagnosing vasculitis in the absence of temporal arteritic damage.