Abstract
A 79-year-old woman presented with difficulty walking and disturbance of consciousness. Magnetic resonance imaging revealed diffuse white matter lesions and abnormal signals along the surface of the brain and sulci. A brain biopsy revealed granulomatous vasculitis with eosinophil infiltration. There was no peripheral blood eosinophilia or evidence of angiitis in other organs, and primary angiitis of the central nervous system (PACNS) with pathological findings of eosinophilic granulomatosis with polyangiitis (EGPA) was diagnosed. Steroids and other immunosuppressant therapies showed only limited effects. PACNS with pathological findings of EGPA is extremely rare, and a prompt brain biopsy is necessary for a diagnosis.