To investigate the relevance of RF in patients with EGPA, we reviewed consecutive patients who were newly diagnosed with EGPA from August 1998 to February 2019 in Keio University Hospital with RF titer at diagnosis available. We divided the patients according to the median level of RF titer of 75 IU/mL and compared clinical features between the two groups. Among 16 patients identified, 8 patients were in the RF high group and the other 8 patients were in the RF low group. All patients in the high RF group were negative for MPO-ANCA, whereas all in the low RF group was positive for MPO-ANCA with a mean titer of 103 IU/mL. The eosinophil count at diagnosis was significantly higher in the RF high group than the RF low group (20001/μL vs 5144/μL, p < 0.01). Gastrointestinal lesion was significantly more frequent in the RF high group, and parenchymal organ lesions, such as heart and renal organ involvement, were frequent in the RF low group. With principal component analysis, RF high and low groups were clearly divided by the combination of eosinophil count, MPO-ANCA titer, gastrointestinal lesions, musculoskeletal symptoms, and disease activity score. Those results suggest EGPA can be divided into two groups in association with RF.Key Points• Our study showed that patients with EGPA can be separated into two groups according to RF titer.• The two subtypes reflect different underlying pathogenesis in EGPA, and the optimal treatment for them may be different.
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