Exploratory classification of clinical phenotypes in Japanese patients with antineutrophil cytoplasmic antibody-associated vasculitis using cluster analysis

A novel patient cluster in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) may be identified in Japan. We performed multiple correspondence and cluster analysis regarding 427 clinically diagnosed AAV patients excluding eosinophilic granulomatosis with polyangiitis. Model 1 included the ANCA phenotype, items of the Birmingham Vasculitis Activity Score, and interstitial lung disease; model 2 included serum creatinine (s-Cr) and C-reactive protein (CRP) levels with model 1 components. In seven clusters determined in model 1, the ANCA-negative (n=8) and proteinase 3-ANCA-positive (n=41) groups emerged as two distinct clusters. The other five myeloperoxidase-ANCA-positive clusters were characterized by ear, nose, and throat (ENT) (n=47); cutaneous (n=36); renal (n=256), non-renal (n=33); and both ENT and cutaneous symptoms (n=6). Four clusters in model 2 were characterized by myeloperoxidase-ANCA negativity (n=42), without s-Cr elevation (<1.3 mg/dL) (n=157), s-Cr elevation (1.3 mg/dL) with high CRP (>10 mg/dL) (n=71), or s-Cr elevation (>= 1.3 mg/dL) without high CRP (<= 10 mg/dL) (n=157). Overall, renal, and relapse-free survival rates were significantly different across the four clusters in model 2. ENT, cutaneous, and renal symptoms may be useful in characterization of Japanese AAV patients with myeloperoxidase-ANCA. The combination of s-Cr and CRP levels may be predictive of prognosis.