Three unusual mimics of primary angiitis of the central nervous system.

To present three rare mimics of primary angiitis of the central nervous system (PACNS). We describe 3 patients with rare diseases that can mimic PACNS at clinical presentation and neuroimaging. We describe the clinical course of these patients and also present a review of the literature regarding these three diagnoses. All 3 patients presented with neurological symptoms and had abnormal findings on neuroimaging suggestive of PACNS. After detailed history, careful review of systems, thorough laboratory workup and consideration of lack of a response to immunosuppressive therapy, PACNS was ruled out with identification of an alternative diagnosis. PACNS is a rare disease and a diagnostic challenge with many differentials. A thorough investigation and awareness of unusual disorders is critical in avoiding misdiagnosis.