Coexisting anti-NMDA and anti-GAD65 antibodies in a patient with autoimmune encephalitis: a case report

Autoimmune encephalitis (AE) typically manifests with a wide range of neuropsychiatric symptoms. Although reports of overlapping antibodies in AE are increasing, their clinical significance remains incompletely understood. Coexisting antibodies may expand the phenotypic spectrum, make it difficult to attribute symptoms to a single disorder, and, in some cases, be associated with more complex disease courses and poorer outcomes. A 56-year-old man with autoimmune encephalitis and overlapping anti-GAD65 and anti-NMDA antibodies is presented. His initial episodes of shouting and muscle contractions were misdiagnosed as psychogenic non-epileptic seizures. After progression to generalized tonic-clonic seizures and ICU admission, cerebrospinal fluid analysis confirmed the presence of both antibodies. Despite pulse methylprednisolone followed by plasmapheresis, his neurological status did not improve, and he died of septic shock. This report highlights diagnostic challenges in AE and suggests that overlapping antibodies may predict a poorer prognosis, necessitating early recognition and management.