LAUSR

Small vessel primary angiitis of the central nervous system is a rare and often severe disease characterized by central nervous system‐restricted inflammatory vasculitis on histopathology. Diagnosis requires brain biopsy for confirmation and is suggested prior to starting immunotherapy when feasible. However, emerging evidence suggests that other neuroinflammatory conditions may have a clinical and radiographic phenotype that mimics small vessel primary angiitis, at times with overlapping pathologic features as well. Such diagnoses, including myelin oligodendrocyte glycoprotein antibody‐associated disease and central nervous system‐restricted hemophagocytic lymphohistiocytosis, can be non‐invasively diagnosed with serum antibody or genetic testing that would prompt different monitoring and treatment paradigms. To determine the ultimate diagnosis of patients who were suspected prior to biopsy to have small vessel primary angiitis, we reviewed the clinical, radiographic, and pathological features of a cohort of patients at a single center undergoing brain biopsy for non‐oncologic indications.