Comparison of the Phenotype and Outcome of Granulomatosis with Polyangiitis Between UK and Japanese Cohorts

Objective. There are differences in the frequencies of antineutrophil cytoplasmic antibodies (ANCA)associated vasculitis subgroups between different geographic regions, and we have reported differences in the phenotype of microscopic polyangiitis between Europe and Japan. In this retrospective observational study, we compared phenotypes and outcomes of granulomatosis with polyangiitis (GPA) between the United Kingdom and Japan. Methods. We identified 128 UK and 82 Japanese patients with GPA diagnosed between 2000 and 2012. We evaluated baseline characteristics including ANCA status and organ involvement, treatment, patient and renal survival, and time to first relapse. Results. Median age at onset was higher in Japan than in the UK (62.2 yrs vs 57.5 yrs, p < 0.01). The proportion of patients with proteinase 3 (PR3)-ANCA was lower in Japan than in the UK (61.0% vs 85.2%, p < 0.01), while the proportion of myeloperoxidase-ANCA was higher in Japan than the UK (34.1% vs 8.6%, p < 0.01). Serum creatinine at diagnosis was lower in Japan than the UK (68.1 mu mol/l vs 101.0 mu mol/l, p < 0.01). Respiratory involvement was more frequent in Japan than the UK (69.5% vs 40.6%, p < 0.01). In both countries, most patients received both glucocorticoids and cyclophosphamide. At 60 months the cumulative survival rates were 87.6% and 94.3% in Japan and the UK, respectively (p = 0.03). At 60 months the cumulative relapse rates were 37.1% and 68.1% in Japan and the UK, respectively (p < 0.01). Conclusion. Japanese patients with GPA were older at disease onset, with less PR3-ANCA positivity, milder renal dysfunction, and more frequent respiratory involvement than UK patients. The relapse-free survival rate was higher in Japan than the United Kingdom.