FRI0204 COMPARISON BETWEEN TRANSMURAL AND ISOLATED (PERI)ADVENTITIAL INFLAMMATION AT TEMPORAL ARTERY BIOPSY: A SINGLE CENTER COHORT OF BIOPSY-POSITIVE GCA WITH LONG TERM FOLLOW-UP
Authors: E. Galli, F. Muratore, L. Boiardi, A. Cavazza, G. Restuccia, L. Cimino, C. Salvarani
Journal: Annals of the Rheumatic Diseases (2020)

Background: Temporal artery biopsy (TAB) showing transmural inflammation is considered the gold standard for the diagnosis of giant cell arteritis (GCA). In some cases, inflammation is confined to periadventitial small vessels and/or the adventitia. However, the clinical significance of this more limited inflammation remains unclear. Up to date, no studies have compared treatment, prognosis and long-term outcomes of patients with transmural inflammation with those of patients with isolated (peri)adventitial inflammation. Objectives: To compare treatment and long-term outcomes of patients with transmural inflammation with those of patients with (peri)adventitial inflammation in a single center cohort of patients with biopsy-positive GCA with long-term follow-up. Methods: All TABs performed for suspected GCA between 1986 and 2013 were reviewed by a single pathologist. Based on the localization of the inflammation, inflamed TABs were classified into 2 categories: transmural inflammation (TMI), with external elastic lamina disruption and extension of the inflammation to the media; (peri)adventitial inflammation (PAI), with inflammation limited to small periadventitial vessels and/or to the adventitia without extension to the media. All medical records of these patients were retrospectively reviewed from the date of TAB to 31 December 2018 or death. Only patients with a follow-up of at least 18 months after GCA diagnosis were included. Cohort characteristics were compared using Wilcoxon rank sum tests for continuous variables and chi-square tests for categorical variables. Kaplan-Meier methods and log-rank tests were used to estimate the rate of development of outcomes. Results: In the study period 254 TMI and 80 PAI were identified. Baseline clinical manifestations and laboratory findings of the 2 cohorts were previously reported (1). Similar frequencies of systemic symptoms, visual manifestations and polymyalgia rheumatica were found in the 2 cohorts. Compared with patients with TMI, those with PAI had a significantly lower frequency of cranial symptoms, abnormalities of TA at physical examination, halo at TA color duplex sonography, lower levels of ESR and CRP and higher frequency of male gender and peripheral arthritis. Large vessel involvement was found in 6/22 (27%) patients with PAI and 32/81 (40%) patients with TMI, p=0.292. 118 patients with TMI and 35 with PAI had a follow-up longer than 18 months and were included for outcome analysis. Median (IQR) follow-up was 79.8 months (52, 115) for patients with TMI and 67.9 (34, 125) for those with PAI, p=0.125. Compared to patients with TMI, those with PAI received a significantly lower initial prednisone dose (35.8±22.0 vs 46.8±15.0 mg, p&lt;0.0001), reached sooner a prednisone dose &lt;10 mg/day (median 4.7 months vs 6.3, p=0.001) and &lt;5 mg/day (median 7.5 months vs 10.3, p=0.005), had a lower cumulative prednisone dose at 1 year (5.7±3.8 vs 7.2±2.3 g, p=0.005) and at the end of the follow-up period (10.0±9.0 vs 12.9±9.6 g, p=0.015). There were no differences in the frequencies of relapses, long-term remission, time to first GC discontinuation and treatment duration between patients with TMI and PAI (p&gt;0.05). Conclusion: Patients with PAI seem to have a disease course similar to those with the transmural pattern, but may require lower GC dosage. Our data confirm that inflammation confined to periadventitial small vessels and/or the adventitia could be considered part of the histopathologic spectrum of GCA. References: [1]Restuccia G, et Al. Small-vessel vasculitis surrounding an uninflamed temporal artery and isolated vasa vasorum vasculits of the temporal artery: Two subsets of giant cell arteritis. Arthritis Rheum. 2011. Disclosure of Interests: None declared