Limbic encephalitis is a condition characterised by an acute or sub-acute onset of memory disorder, associated with seizures and psychiatric manifestations. Investigations such as brain MRI usually reveal a high intensity signal in the medial temporal lobe and cerebrospinal fluid analysis shows mild pleocytosis and oligoclonal bands. It may occur in association with cancer, infection, or as an isolated clinical condition, often accompanying autoimmune disorders. Immune-mediated limbic encephalitis is now subclassified according to the presence and type of autoantibodies, which has significant consequences regarding the effectiveness of treatment and prognosis. Glutamic acid decarboxylase (GAD) is an enzyme that catalyses glutamic acid into gamma aminobutyric acid. Anti-GAD antibodies are associated with different neurological and non-neurological disorders, but only a few cases of limbic encephalitis associated with anti-GAD antibodies have been reported in the literature, most of them non-paraneoplastic. Here, we report the case of a young female patient with a medical history of psoriasis who developed an acute onset and chronic evolution of anterograde amnesia, associated with drug-resistant epilepsy. Brain MRI showed hyperintensity in the medial temporal lobes and the biochemical studies revealed intrathecal synthesis of anti-GAD antibodies. Screening tests for tumours were negative. Despite antiepileptic drugs, intravenous immunoglobulins and immunosuppressive treatment, the patient did not show clinical improvement and one year later, she continues to present refractory temporal epilepsy and cognitive deficits.
Keywords: glutamic acid decarboxylase; immunotherapy; limbic encephalitis; paraneoplastic antibody.