421. Giant Cell Arteritis during treatment with Tocilizumab
Creators: name: Yousef Alammari1, 3
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Presentation of Cases:</strong> We present four cases (table 1) with giant cell arteritis (GCA) presenting for the first time (cases 1 and 2) or relapsing (cases 3 and 4) all with normal ESR and CRP during tocilizumab (TCZ) therapy. <strong>Case 1:</strong> 71-year-old female with a 7-year history of steroid-dependent polymyalgia rheumatica (PMR). TCZ was added as a steroid-sparing agent. 19 months later, she developed a new onset GCA with ischemic stroke, confirmed on temporal artery ultrasound (TA-US+) and biopsy. She was treated with steroids, and TCZ was switched to Ustekinumab (UST), which resulted in clinical remission. <strong>Case 2:</strong> 70-year-old female with a 14-year history of rheumatoid arthritis (RA) who failed three anti-TNF agents. 11 months following switching to TCZ to control her refractory RA, she developed cranial GCA (TA-US+) treated with high dose steroids. Her TCZ was switched to UST and remained in remission. <strong>Case 3:</strong> 62-year-old male with well-controlled RA on Methotrexate (MTX) and Adalimumab (ADA) who developed GCA. He was treated with high dose steroids and switched to UST and remained in remission for over three years. RA subsequently flared, prompting a switch from UST to TCZ. After 2 months he developed a relapse of cranial GCA (TA-US+). He was treated with high dose steroids, and his TCZ was switched to Abatacept (ABA), with RA and GCA remission. <strong>Case 4:</strong> 70-year-old female with a history of PMR who developed cranial GCA and large-vessel vasculitis (LVV), which was successfully treated with a high dose steroid and UST. GCA flared 23 months later, prompting a switch to TCZ, resulting in remission. However, after 22 months on TCZ, she had GCA relapse with active LVV (and sacroilitis) on PET-CT, treated with switch of TCZ to ADA. <strong>Diagnostic testing:</strong> Normal ESR and CRP in each patient at diagnosis of new/relapsing GCA on TCZ. TA-US, TA biopsy and PET-CT as above. <strong>Differential &amp; Final Diagnosis</strong> The final diagnosis was GCA. Differential: primary headache syndromes. <strong>Discussion of Management:</strong> T-lymphocytes subsets, both Th1 and Th17, are implicated in the pathogenesis of GCA. They are considered to drive two distinct inflammatory pathways.<sup>1</sup> TCZ inhibits the interleukin-6 receptor, which contributes to Th17 differentiation but not the Th1 cell pathway.<sup>2</sup> TCZ is the first agent licensed for the treatment of GCA.<sup>3</sup> UST blocks both IL-12 and IL-23 activity, which are involved in developing Th1 and Th17 responses, respectively.<sup>4</sup> ABA, a T-cell modulator, also contributes to inhibiting both Th1 and Th17 differentiation. This prompted consideration of these alternative agents in TCZ refractory patients. <strong>Conclusions:</strong> These cases demonstrate that GCA may present for the first time or relapse during TCZ treatment. The diagnosis of GCA in this setting is hindered by the normal acute phase reactants typically found in TCZ-treated patients, even in the presence of active rheumatic disease or systemic infection. Patients treated with TCZ (and their primary care providers) should be counselled regarding the unreliability of acute phase markers during TCZ treatment. Vigilance for clinical evidence of relapse should be maintained in TCZ-treated patients and a low threshold imposed for performing radiologic investigations to evaluate disease activity. <strong>Disclosures:</strong> None