MPO and microscopic polyangiitis: PR3-ANCA-positive AAV tends to involve head and neck symptoms more often than MPO-ANCA-positive AAV, whereas MPO-ANCA-positive AAV tends to feature severe renal damage [1], which suggests that PR3-ANCA-positive AAV almost corresponds to GPA, whereas MPO-ANCA-positive AAV almost corresponds to MPA, as included in the above-listed classification criteria [24,25,26,28].