A primary systemic vasculitis of small- and some medium-sized vessels. It is characterized by a tropism for kidneys and lungs, positive association with anti-neutrophil cytoplasmic antibodies (ANCA), and a paucity of immunoglobulin deposits in vessel walls.
Diseases of any component of the brain (including the cerebral hemispheres, diencephalon, brain stem, and cerebellum) or the spinal cord.