BackgroundLimbic encephalitis (LE) is a rare variant of autoimmune encephalitis. It often manifests with subacute neuropsychiatric symptoms of agitation, delusions, variable seizure semiology, and short-term memory loss. Seronegative limbic encephalitis can pose a diagnostic conundrum owing to its inadequately understood pathophysiology.Case presentationWe report a rare case of a young male with subacute neuropsychiatric manifestations of delusions, agitations and seizures. He was diagnosed with seronegative limbic encephalitis (SNLE). Brain MRI demonstrated bilateral Claustrum sparing sign. An EEG showed continuous left-sided epileptiform discharges in periodic to predominantly left middle temporal. Patient condition gradually improved with pulsed methylprednisolone, intravenous immunoglobulins and anti-seizure medications.ConclusionClaustrum remains one of the least understood neuroanatomical structures. Claustrum sign has been reported in febrile infection-related epilepsy syndrome (FIRES), LE, and autoimmune refractory epilepsy. To the best of our knowledge, we report the first case in literature with Claustrum sparing sign in seronegative Limbic Encephalitis. Further experimental models and researches are warranted to better understand the unique function of the claustrum and unravel possible other attributable auto-antibodies, which could alter treatment and prognosis.