New-onset giant cell arteritis with lower ESR and CRP level carries a similar ischemic risk to other forms of the disease but has an excellent late prognosis: a case–control study

Introduction Biopsy-proven giant cell arteritis (GCA) occasionally presents without acute-phase reaction. In this setting, GCA may be initially overlooked and glucocorticoid treatment unduly delayed, potentially increasing ischemic risk. Patients and methods From an inception cohort of patients with newly diagnosed, biopsy-verified GCA, we retrieved all cases without elevation of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level before starting glucocorticoid treatment. We compared the baseline features and outcomes of these patients and two additional patients recruited after GCA diagnosis with those of 42 randomly selected patients with high baseline ESR and CRP. Results Of 396 patients, 14 (3.5%) had lower baseline values of both ESR and CRP. Lower baseline ESR and CRP were associated with fewer American College of Rheumatology criteria met ( p < 0.001, 95% CI − 1.1; − 0.9), and less jaw claudication ( p = 0.06, 95% CI 0.8; 44.9), but similar rates of permanent blindness ( p = 1.0). Patients with lower ESR and CRP also showed obvious differences regarding mean blood cell counts and mean hemoglobin level, but also less anti-cardiolipin antibody positivity (p = 0.04, 95% CI 0.8; ∞ ) and hepatic cholestasis ( p = 0.03, 95% CI 1.0; 422). Patients with lower ESR and CRP had fewer GCA relapses ( p = 0.03, 95% CI − 1.1; − 0.1), fewer glucocorticoid-induced complications ( p = 0.01, 95% CI − 2.0; − 0.1), and successfully stopped glucocorticoids sooner than the other patients (18.3 months vs 34 months in average, p = 0.02, 95% CI − 27;− 0.9). Conclusion Biopsy-proven GCA presenting with lower ESR and CRP is not an exceptional occurrence. It is clinically less typical but carries similar ischemic risk to other forms of the disease. Conversely, the late GCA prognosis of these patients is excellent.