MOG antibody disease manifesting as progressive cognitive deterioration and behavioral changes with primary central nervous system vasculitis.

We report a 60-year-old male with anti-myelin oligodendrocyte glycoprotein (MOG) antibody who developed progressive cognitive deterioration and behavioral changes, with no other focal signs, over 9 months. MRI showed numerous T2-hyperintense lesions with partial contrast enhancement in white and grey matter of cerebrum, cerebellum and spinal cord. A brain biopsy revealed perivascular inflammatory cell infiltration, disturbed vascular continuity and no demyelination, indicative of a lymphocytic pattern of primary CNS vasculitis (PCNSV). Contrast enhancement disappeared after immunotherapy; however, cognitive impairment was not improved. Neurologists should note that MOG antibody disease can present as immunotherapy-resistant progressive cognitive impairment with PCNSV-like histopathology.