Successful treatment of anti-LGI1-associated autoimmune encephalitis with efgartigimod: A case report and literature review

RATIONALE: Anti leucine rich glioma inactivated 1 (LGI1)- associated autoimmune encephalitis (AE) is the common form of AE, The treatments for AE may cause many adverse effects and some treatments rely on limited blood resources. Monoclonal antibodies directed against neonatal crystallizable fragment receptor (FcRn), efgartigimod, accelerate autoantibody degradation by blocking IgG recirculation. The efficacy of efgartigimod has been demonstrated in myasthenia gravis. However, there are few case reports on the treatment of anti-LGI1-associated AE with efgartigimod. In this study, we present the case of a patient with anti-LGI1-associated AE who was treated with efgartigimod successfully. PATIENT CONCERNS: A 64-year-old female patient presented with decline in short-term memory and limb tremor. Cranial magnetic resonance imaging (MRI) scan showed hyperintensity and swelling in the medial aspect of the right temporal-occipital lobe on T2- and FLAIR-weighted sequences, without obvious enhancement lesions. The anti-LGI1 antibody titer in serum and CSF was positive. DIAGNOSES: The patient was diagnosed with anti-LGI1-associated AE. INTERVENTIONS: Initially, the patient received methylprednisolone pulse therapy. Levetiracetam and oxcarbazepine were both administered orally in the meantime. Following treatment failure, efgartigimod was administered once a week for 3 weeks. OUTCOMES: After treatment, the patient's limb tremors ceased and her memory improved. The level of anti-LGI1 antibody titer in serum decreased, and the abnormal signals on the MRI attenuated. LESSONS: Efgartigimod is an effective treatment for anti-LGI1-associated AE. This study presents a new approach to treat anti-LGI1-associated AE. However, further research is needed to establish the optimal dosage and frequency of efgartigimod, and to clarify its long-term safety and efficacy.