According to studies, either MPO-ANCAs or PR3-ANCAs are present in 90% of patients with GPA, MPA, or EGPA [18,19]; on the contrary, our cohort consists of 65.8% seropositive and 34.3% seronegative patients, indicating that more diagnoses were made based on clinicopathological features rather than a positive ANCA test. The gene discussed is MPO; the disease is microscopic polyangiitis.