PRTN3 and Decreased total leukocyte count: Laboratory investigations revealed leukopenia with a white blood cell count (WBC) of 2,600 cells/μL, neutropenia with an absolute neutrophil count (ANC) of 900 cells/μL, an elevated erythrocyte sedimentation rate (ESR) of 47 mm/hour, presence of lupus anticoagulant, low complement component 3 (C3) (85 mg/dL), a normal coagulation profile, absence of antinuclear antibody (ANA), absence of cardiolipin antibody, presence of perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) against myeloperoxidase (MPO), and absence of antiproteinase 3 (anti-PR3) antibody.