P296 Giant cell arteritis/large vessel vasculitis with normal inflammatory markers: a case series of 15 patients in south Manchester

Abstract

Background/Aims An elevated ESR is a criterion for giant cell arteritis (GCA) in the 1990 ACR classification. An international case series of GCA with normal inflammatory markers has been described. We describe characteristics and estimate the incidence of patients with GCA/large vessel vasculitis (LVV) with normal or minimally elevated inflammatory markers in south Manchester. Methods Temporal-axillary artery ultrasound (TAUS) has been the first line investigation modality in the local GCA fast track pathway (FTP) since 2019. TAUS, performed between April 2019 and May 2021, were reviewed. Clinical notes were reviewed if patients had scan findings positive for hypoechoic halos. Basic demographics and clinical details were further collected for cases with ESR <50mm/hr or CRP <20mg/dL to characterise their clinical profile. Results 15 patients had positive TAUS with ESR <50mm/hr or CRP <20mg/dL. 10 patients were male (66.7%) and 5 were female (33.3%). 14 (93.3%) patients were of Caucasian race, while 1 was of African Black origin (6.7%). Median age at presentation was 66 years (63-74). Median BMI was overweight at 29kg/m2. Headache was the most common symptom in 13 patients (86.7%), followed by jaw and ocular complaints in 7 patients each (46.7%), and polymyalgia rheumatica in 3 patients (20%). Fevers and weight loss were each noted in 1 patient (6.7%). Median duration of symptoms before referral to our centre was 21 days (7-51). Formal ophthalmology assessment did not identify any patient with ocular damage. Median ESR was 17mm/hr (10- 21) and CRP 3.5g/dL (2-4.8). Median duration of steroids before TAUS was 0 days. In 1 patient, diagnosis of LVV was further confirmed by PET scan, while in another, it was further confirmed by MR and CT aortogram. 2 cases (13.3%) were relapses of GCA - 1 of which was previously confirmed on histology. All patients indicated symptom response to corticosteroids. Repeated TAUS in 8 patients noted 3 resolution, 3 improvement, 1 unchanged and 1 slight worsening. 6 (40%) patients required DMARDs (2 tocilizumab and 4 methotrexate). Conclusion TAUS facilitates early diagnosis of atypical GCA/LVV in patients who present with relatively normal inflammatory markers - our time-to-scan from steroid treatment was a median of 0 days. Early definitive treatment may explain the absence of ophthalmic morbidity amongst our patients. With an estimated population of 137,000 in south Manchester, these 15 cases suggest an incidence of atypical GCA/LVV to be 5.5 per 100,000 people. The elevated median BMI of our patients challenges the traditional notion that baseline ESR should be adjusted in patients with increased body mass. Relatively prolonged symptom duration (median 21 days) before referral to our FTP also challenges the notion that normal inflammatory markers in GCA/LVV reflects the window period of early presentation before disease evolution with subsequent inflammatory rise. Disclosure E.P. Chua: None.