Patients with signs and symptoms of pulmonary-renal syndrome caused by Wegener's granulomatosis present, in their vast majority, positivity for antineutrophil cytoplasm antibodies with c-ANCA pattern anti-PR3.10 Patients with microscopic polyangiitis can present positive ANCA with perinuclear pattern (pANCA) anti-MPO or cytoplasmic pattern (cANCA) anti-PR3. This evidence concerns the gene MPO and microscopic polyangiitis.