Rheumatoid factor is associated with systemic relapse in eosinophilic granulomatosis with polyangiitis.

Systemic relapse remains a major cause of morbidity in eosinophilic granulomatosis with polyangiitis (EGPA), but widely available prognostic markers are lacking. We retrospectively assessed 83 EGPA patients with rheumatoid factor (RF) tested at diagnosis. Systemic relapse was defined as new or worsening systemic disease activity and treatment escalation, excluding isolated asthma and rhinosinusitis exacerbations. RF-positive patients (45.8%) had higher C-reactive protein levels, more frequent mononeuritis multiplex, and more frequent systemic relapses (39.5% vs. 2.2%, q = 0.002). In the penalised Cox analysis, RF positivity was associated with shorter time to systemic relapse (HR 10.05, 95% CI 2.43-92.57; p < 0.001) and remained associated after adjustment for MPO-ANCA and treatment intensity. RF positivity may support closer surveillance in EGPA.