Right arm weakness and mouth deviation as a presentation of Primary Angiitis of the Central Nervous System treated with rituximab: A case-report.

Introduction: Primary Angiitis of the Central Nervous System (PACNS) is a rare form of vasculitis that solely affects the Central Nervous System (CNS). Its presentation varies widely from a simple headache to a stroke-like presentation. PACNS management is divided into an induction phase, which includes corticosteroids, cyclophosphamide and rituximab, and a maintenance phase which includes: methotrexate, mycophenolate mofetil, rituximab and azathioprine. Case presentation: A 31-year-old male presented to the emergency department due to an episode of right arm weakness and left-sided facial weakness. Brain Magnetic Resonance Imaging (MRI) would show an ischemic change in the frontal and parietal lobes. A biopsy was done, which showed inflammatory infiltrates consistent with Primary Angiitis of the Central Nervous System. The patient was started on rituximab and showed improvement. Clinical discussion: In this case, PACNS presented as episodic right arm weakness and left sided facial weakness. Gold standard for diagnosis is a biopsy from the inflamed region of the CNS that shows lymphocytic infiltration in a granulomatous pattern. Conclusion: Despite its rarity, PACNS is a cause of morbidity if not caught and managed early. Therefore, considering PACNS in the differential diagnosis of a young patient with a history of frequent episodic neurological dysfunction is appropriate. Ischemic patterns on MRI further increase the index of suspicion around PACNS Confirmation of the diagnosis via biopsy from the inflamed region is the most accurate method.