Comparison of biopsy-proven giant cell arteritis in North America and Southern Europe: a population-based study

OBJECTIVES: To compare clinical characteristics, treatment and prognosis of two population-based cohorts of patients with biopsy-proven giant cell arteritis (GCA) from Olmsted County, Minnesota, USA (Olmsted cohort) and the Reggio Emilia area, Northern Italy (Reggio cohort). METHODS: All patients residing in Olmsted County and the Reggio Emilia area with a new diagnosis of biopsy-proven GCA in 1986-2007 were retrospectively identified. Patients were followed from GCA diagnosis to death, migration or September 2011. RESULTS: The study included 110 patients in the Olmsted and 144 in the Reggio cohort. Compared with the Olmsted cohort, patients from the Reggio cohort had longer duration of symptoms prior to diagnosis (median 1.4 months vs. 0.7, p<0.001) and were younger (mean 74.6 years vs. 77.8, p=0.002), more likely to have cranial symptoms (93% vs. 86%, p=0.048), permanent vision loss (21% vs. 6%, p=0.001) and systemic symptoms (67% vs. 46%, p=0.001). ESR and CRP were higher (mean 88 mm/h vs. 73, and 89.0 mg/L vs. 35.2, both p<0.001) in the Reggio cohort. Patients from the Olmsted cohort received a higher initial prednisone dose (mean 53.6 mg/day vs. 49.5, p=0.001). There were no differences in relapse rates, cumulative glucocorticoid (GC) dosages at 1, 2 and 5 years, and time to first GC discontinuation. CONCLUSIONS: Geographical, genetic and/or environmental factors may contribute to the different clinical features at onset of GCA observed in this study.