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Limbic encephalitis is characterised by subacute development of short-term memory loss, seizures, confusion and psychiatric features.1 Paraneoplastic limbic encephalitis is generally associated with small cell lung cancer (SCLC), and around 50% of patients harbour Hu, CV2/CRMP5 or amphiphysin antibodies.1 Recently, antibodies against voltage-gated potassium channels (VGKC-abs) were identified as a new marker of a non-paraneoplastic, immunotherapy-responsive form of limbic encephalitis.2,3 However, the presence of VGKC-ab does not exclude a paraneoplastic cause of limbic encephalitis.1
We described previously a new antibody called anti-glial nuclear antibody (AGNA), a marker of SCLC shown to be closely associated with paraneoplastic Lambert–Eaton myasthenic syndrome (LEMS).4 Here we report on two patients with paraneoplastic limbic encephalitis associated with SCLC and VGKC-ab who also presented AGNA.
The presence of AGNA was assessed by immunohistochemistry on frozen sections of paraformaldehyde-fixed rat cerebellum in nine patients with limbic encephalitis and SCLC with (n = 2) or without (n = 7) VGKC-ab, and in seven patients with non-paraneoplastic limbic encephalitis and VGKC-ab. To confirm AGNA reactivity, an immunohistochemical competition assay was performed as described previously.4 VGKC-abs were detected by radioimmunoprecipitation (cutoff value: 100 pmol/l).2
A middle-aged man was admitted to hospital with a 2-week history of behavioural changes and generalised seizures. A neurological examination showed short-term memory loss, confusion and aphasia. Electroencephalography showed slowing in the left temporal lobe. Magnetic resonance …