Association of rheumatoid factor with vasculitic manifestations and distinct clinical patterns in eosinophilic granulomatosis with polyangiitis: a multicenter observational study.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a heterogeneous disease characterized by overlapping eosinophilic and vasculitic manifestations, and reliable markers reflecting disease phenotype and prognosis remain limited. In this study, we aimed to evaluate the clinical and prognostic significance of rheumatoid factor (RF) positivity in patients with EGPA and to explore phenotypic patterns using cluster analysis. Clinical features, laboratory findings, treatment and outcome data of 50 patients with EGPA from three tertiary referral centers were collected retrospectively and included in the study. RF positivity was defined as titers > 3× the upper limit of normal. RF positivity was observed in 36% of patients and was significantly associated with mononeuritis multiplex (p = 0.03, OR 3.8%95 CI [1.1-12.8]), purpura (p = 0.003, OR 6.8%95 CI [1.8-25.6]), higher C-reactive protein levels at diagnosis (p = 0.014), and shorter relapse-free survival (37.8 ± 8.5 vs. 135 ± 12.8 months, log rank p < 0.001). ANCA status was not associated with relapse risk or overall disease severity. Exploratory cluster analysis identified three phenotypic patterns, including two higher-risk patterns characterized by vasculitic neuropathy and cardiomyopathy, both associated with higher relapse rates and RF positivity, and a third subgroup with milder disease and the highest prevalence of upper respiratory tract involvement. These findings suggest a potential association with RF positivity and a more inflammatory and relapse-prone disease course in EGPA and provide additional clinical information. Integrating RF with key clinical features may improve risk stratification and longitudinal management. Prospective studies in larger cohorts are needed to validate these observations.