PRTN3 and microscopic polyangiitis: Anti-PR3 autoantibodies [cytoplasmic ANCA (c-ANCA)] are positive in about 90% of patients with active Wegener granulomatosis, and anti-MPO autoantibodies [perinuclear ANCA (p-ANCA)] are typically detected in about 80% of patients with active MPA (54, 55).