Overlapping autoimmune encephalitis with tripartite autoantibody positivity (NMDAR, GFAP, mGluR5) associated with papillary thyroid carcinoma: a case report.

BACKGROUND

Autoimmune encephalitis (AE) with concurrent triple neuronal/glial autoantibody positivity is exceptionally rare, and its correlation with thyroid carcinoma remains undocumented. We report for the first time a case of overlapping syndrome characterized by co-existence of anti-N-methyl-D-aspartate receptor (NMDAR), anti-glial fibrillary acidic protein (GFAP), and anti-metabotropic glutamate receptor 5 (mGluR5) antibodies, association with papillary thyroid carcinoma (PTC).

CASE PRESENTATION: A 50-year-old Chinese Han woman presented with headache, mental behavioral abnormalities, and memory loss, which further developed with fever, involuntary movements, and impaired consciousness. Cerebrospinal fluid (CSF) examination revealed lymphocytic-predominant pleocytosis and elevated protein levels. CSF was positive for the three antibodies mentioned above. After treatment with methylprednisolone, rituximab, and immunoadsorption with staphylococcal protein A column (SPA-IA) treatment, her consciousness became clear and mental state returned to normal, except for memory loss during the onset of illness. Whole-body nuclear PET/CT detected thyroid tumor. She underwent radical thyroidectomy and resumed normal life without recurrence during an 18-month follow-up.

CONCLUSION

This is the first reported case of this unique triad, highlighting the importance of considering underlying malignancy in patients with multiple neuronal/glial antibody co-existences.