A rare case of anti-LGI1 limbic encephalitis with concomitant positive NMDAR antibodies

N-methyl-D-aspartate receptor (NMDAR) and leucine-rich glioma-inactivated 1 (LGI1) antibodies define the most prevalently recognized autoimmune encephalitis syndromes, while the simultaneous occurrence of both conditions has hardly been published before.

We report the case of a 67-year-old patient who presented with generalized tonic-clonic seizures (GTCS) followed by behavioral changes, psychosis, sleep disorders, decreased consciousness, and faciobrachial dystonic seizures. Ancillary findings included serum hyponatremia and imaging evidence of high-intensity lesions within bilateral medial temporal lobes on T2-weighted fluid attenuation inversion recovery. Both LGI1 and NMDAR antibodies were positive in serum and cerebral spinal fluid using transfected cell based assays. Despite prominent clinical features of anti-LGI1 limbic encephalitis (LGI1-LE), the patient also exhibited overlapping symptoms of anti-NMDAR encephalitis, like early-onset GTCS, which might be related to the concomitant positive NMDAR antibodies.

We report a rare case of LGI1-LE with overlapping symptoms and simultaneous positive NMDAR antibodies. It is necessary to evaluate the presence of NMDAR antibodies in certain LGI1-LE patients with unusual symptoms. However, caution should be exercised in interpreting the observation, given the fact of a single-case study.