Autoimmune encephalitis with coexisting antibodies to GABABR, GAD65, SOX1 and Ma2.

Background: Autoimmune encephalitis (AE) is a disease caused by an abnormal reaction between the body's autoimmunity and the central nervous system, in which the abnormal immune response targets antigenic components within or on the surface of neuronal cells. The main manifestations are mental and behavioural changes, cognitive impairment, impaired consciousness, seizures, movement disorders, etc. Most cell surface antibodies respond well to immunotherapy, intracellular antibodies, on the other hand, are usually associated with more tumours and are relatively difficult to treat with a poor prognosis. In recent years, autoimmune encephalitis that is positive for multiple anti-neuronal antibodies has been gradually recognized in the clinic, with complex and varied clinical manifestations, especially in combination with malignant tumours, which have worse treatment and prognosis. Current clinical studies on the coexistence of multiple anti-neuronal antibodies in patients with AE are mainly disseminated case reports. Patients with AE in which four anti-neuronal antibodies coexist are even rarer.

Case presentation: We report a patient who initially presented with an irritating dry cough and hyponatraemia and a chest CT suspicious for malignancy, followed by progressive deterioration of persistent status epilepticus, consciousness and cognitive deficits, and psycho-behavioural abnormalities. Serum and cerebrospinal fluid antibodies against neuronal surface or intracellular antigens were detected using a cell-based assay (CBA) method. Serum and cerebrospinal fluid were found to be positive for anti-GABABR, GAD65, SOX1 and Ma2 antibodies. And a definitive diagnosis of small cell lung cancer was made by immunohistochemistry. He eventually received gammaglobulin, steroid pulsed therapy and tumour chemotherapy.

Conclusions: The coexistence or overlap of multiple anti-neuronal surface antibodies with anti-neuronal intracellular antibodies is rare and increases the likelihood of underlying malignancy. Elucidating the impact of individualized immunotherapy and coexisting antibodies on the clinical presentation of patients has the potential to improve long-term prognosis.