Background/Purpose: Temporal arteritis (TA) classically presents as a large-vessel vasculitis in older adults with cranial ischemic symptoms. However, in younger patients or in the presence of eosinophilia, alternative etiologies must be considered.

Methods: We conducted a retrospective, multicenter, descriptive study that included patients with 1) confirmed temporal arteritis, either by histologic confirmation or by the presence of typical clinical symptoms combined with imaging abnormalities, and 2) pretreatment blood eosinophilia >1000/mm3. We also performed a literature review to identify additional cases of eosinophilia-associated temporal arteritis (EoTA). Finally, unsupervised hierarchical clustering was used to classify patients into subgroups to capture the full spectrum of EoTA.

Results: A total of 78 patients were included, i.e. 40 original cases and 38 from the literature review. The median age was 59 years [IQR 41.2-69.8] and 73% were male. The diagnosis of TA was based on histology in 85% of patients, while 33% also had imaging abnormalities.Constitutional symptoms were reported in 63%, headache in 42%, TA induration in 29%, jaw claudication in 26%, and ocular ischemic events in 10%. Other manifestations included pulmonary (47%) and sinonasal (32%) involvement, and peripheral neuropathy (28%). Median eosinophil count was 3500/mm3 [IQR 1800–7370], CRP was 28.8 mg/L [5.0–94.8], and 33% were ANCA positive, predominantly MPO-ANCA. Temporal artery biopsies showed eosinophilic and mononuclear cell infiltration in 69% and 53%, respectively, giant cells in 25%, and internal elastic lamina fragmentation in 40%.Overall, 71% of patients met EGPA criteria, 53% met GCA criteria and 32% met both criteria according to the 2022 ACR/EULAR classification. In addition, 29% of patients were classified as hypereosinophilic syndrome (SHE).First-line therapy consisted of glucocorticoids (GC) in 87%, in combination with immunosuppressive agent in 32% (conventional synthetic DMARDs in 18, biologic DMARDs in 5, eosinophil-targeting biologics in 4). At 6 months, 16 (27%) were in remission, 36 (61%) were GC-dependent, 2 (3%) were refractory, 5 (8.5%) had relapsed, while 19 (24%) did not reach the 6-month follow-up.Cluster analysis identified four distinct groups. Cluster 1 (23%) included young men with isolated TA, low acute phase reactants, consistent with juvenile TA and Kimura disease, and had the highest remission rate (58%). Cluster 2 (32%) included middle-aged patients with systemic involvement, mainly cardiovascular, moderate CRP levels, consistent with HES, and showed frequent GC dependence (82%) and relapses (9%). Cluster 3 (15%) was characterized by older patients with typical features of GCA, with frequent GC dependence (78%). Cluster 4 (29%) included patients with sinonasal involvement, asthma and mononeuritis multiplex, high eosinophil counts and positive MPO-ANCA, consistent with EGPA and showed frequent GC dependence (82%).

Conclusion: Eosinophilia-related TA is a heterogeneous entity at the intersection of GCA, EGPA, HES, and localized TA. While systemic forms resemble EGPA or SHE, others, especially in younger patients, represent benign forms.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/temporal-arteritis-revealing-eosinophilic-diseases-a-multicenter-retrospective-study-literature-review-and-combined-cluster-analysis/