Morvan syndrome associated with LGI1 antibody: a case report

BACKGROUND: Morvan syndrome (MoS) is a rare autoimmune syndrome associated with antibodies against two kinds of potassium channel proteins, contactin associated protein-like 2 (CASPR2) and leucine-rich glioma inactivated protein 1 (LGI1). MoS patients with only LGI1-antibody seropositivity have rarely been reported. Here, we describe a 64-year-old male MoS patient with only LGI1-antibody seropositivity. CASE PRESENTATION: A 64-year-old male patient was referred to our hospital due to limb pain, widespread myokymia, insomnia, constipation, and hyperhidrosis for 1 month. The patient was diagnosed with MoS based on the clinical symptoms and positive LGI1-antibody in serum. He was treated with intravenous immunoglobulin (IVIG), intravenous methylprednisolone followed by oral prednisone, and other drugs for symptomatic relief. Several days later, myokymia and insomnia symptoms improved. After 60 days of follow-up, all the drugs had been stopped for 2 weeks, and the patient achieved complete remission without any medical side effects. CONCLUSION: We report the clinical characteristics of a Chinese MoS patient with only LGI1-antibody seropositivity, and further support the view that non-neoplasm MoS patients respond well to immunotherapy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12883-021-02205-9.