Background/Purpose: Takayasu arteritis (TAK) and giant cell arteritis (GCA) belong to the large vessel vasculitis group. Differences between the two diseases have been reported based on age, clinical presentation, and HLA. ACR/EULAR classification criteria for GCA have been reported, but no pathological criteria for the temporal artery (TA) have been proposed. Pathologically, inflammation of the aorta in TAK starts from the adventitia and inflammation of the temporal artery (TA) in GCA starts from the tunica media, indicating different sites of inflammation in the two diseases. Therefore, it is important to classify TAK and GCA based on pathological findings rather than distinguishing between them based on age. In this study, it was examined whether there is a difference in the presence or absence of aortitis depending on the site of inflammation of the TA (presence or absence of adventitial inflammation) in cases diagnosed with GCA.

Methods: The study included patients admitted to our hospital from 2004 to 2023, who underwent temporal artery biopsy (TAB) and contrast-enhanced thoraco-abdominal computed tomography, and were diagnosed with GCA. According to the pathology of the TAB, the patients were divided into two groups: those with (Ad+ group) and without (Ad- group) adventitial inflammation. In those two groups, clinical symptoms, laboratory findings, and the presence of aortitis were compared between the groups.

Results: Thirty-two patients were included in the study, 21 in the Ad+ group and 11 in the Ad- group. The median age in the Ad+ and Ad- groups was 73 and 69 years, respectively (p=0.010), the frequency of clinical findings were as follows: fever (52.4% vs. 36.4%, p=0.472), headache (81.0% vs. 90.9%, p=0.637), polymyalgia rheumatica (PMR) symptoms (23.8% vs. 36.4%, p=0.681), and TA symptoms (42.9% vs. 81.8%, p=0.061). Blood test findings (median values) showed no significant differences in WBC (7,900 /µl vs. 7,800 /µl, p=0.984) or CRP (9.60 mg/dl vs. 9.26 mg/dl, p=0.736); however, ALP levels in Ad+ group were lower than those in the Ad- group (244 U/L vs. 446 U/L, p=0.009). The frequency of aortitis in the Ad+ group was significantly higher than in the Ad- group (81.0% vs. 27.3%, p=0.006). The initial dose of glucocorticoid (GC) tended to be higher in the Ad+ group (1.0 mg/kg vs. 0.6 mg/kg, p=0.066).

Conclusion: In this study, the Ad- group may have true GCA and the Ad+ group may have TAK; it may be important to distinguish between GCA and TAK based on TAB pathology rather than age.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/frequency-of-large-vessel-vasculitis-in-giant-cell-arteritis-with-and-without-adventiitis-of-temporal-artery-is-the-presence-of-temporal-arteritis-sufficient-to-diagnose-giant-cell-arteritis/