A Rare Case of Central Nervous System Vasculitis in a Patient with Perinuclear Antineutrophil Cytoplasmic Antibodies-associated Interstitial Lung Disease.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic necrotizing inflammation of the small vessels. Central nervous system (CNS) ANCA-associated vasculitis is a rare manifestation of AAV. Three mechanisms of AAV affecting the CNS have been reported which include contiguous granulomatous invasion from nasal and paranasal sinuses, remote granulomatous lesions, and vasculitis of small vessels. Chronic hypertrophic pachymeningitis (CHP) is the meningeal-site involvement in AAV caused by granulomatous inflammation in the dura mater. We present a case of pachymeningitis manifested with slowly progressive cognitive dysfunction, leptomeningeal enhancement on MRI, and necrotic vessels with surrounding inflammation on biopsy. This case represents a rare development of subsequent CNS AAV in a patient with ANCA-associated interstitial lung disease treated with rituximab with a resolution of leptomeningeal enhancement on a follow-up magnetic resonance imaging (MRI).