Guillain-Barré syndrome triggered by West Nile virus infection in Missouri's 2025 outbreak.

A man in his 50s with poorly controlled diabetes and chronic kidney disease presented with rapidly progressive bilateral facial diplegia 1 week after hospitalisation for pneumonia. Examination demonstrated symmetric lower motor neuron facial weakness without limb involvement; reflexes were 1+ throughout. Brain and internal auditory canal MRI were unremarkable. Cerebrospinal fluid showed albuminocytologic dissociation (protein 151 mg/dL, WBC 3 /mm³). Serum antiganglioside antibody testing was positive for GM2 IgG at 72 IV. CSF infectious studies were positive for West Nile virus IgM (3.07) and IgG (2.81), confirming acute neuroinvasive infection during Missouri's 2025 outbreak. The patient was treated with intravenous immunoglobulin and showed progressive improvement in facial strength, eye closure and speech, with continued recovery at 4 weeks. This case emphasises West Nile virus as a potential precipitant of facial diplegic Guillain-Barré syndrome.