In addition, neutropenia (absolute neutrophil count <1500/μL) (4/25; 16%), C3 hypocomplementemia (13/25; 52%), C4 hypocomplementemia (3/25; 12%), positive ANA test (14/25; 56%), positive ANCA test (21/25; 85%) with perinuclear pattern (9/21, 43%), positive anti-MPO antibodies (23/25; 92%), and positive anti-PR3 (7/25; 28%) antibodies were observed. The gene discussed is MPO; the disease is neutropenia.