RESUMO
BACKGROUND: To identify clinical and paraclinical differences between anti-voltage-gated potassium channel (VGKC)-complex seropositive patients with and without anti-leucine-rich glioma-inactivated protein 1 (LGI1)/contactin-associated protein-like 2 (CASPR2) antibodies (Abs). METHODS: We performed a retrospective analysis of 50 anti-VGKC-complex seropositive patients from January 2013 to September 2016, and tested them for anti-LGI1/CASPR2 Abs. Comparative analysis was performed between anti-LGI1/CASPR2 seropositive and 'double negative' patients. RESULTS: Seven patients had anti-LGI1/CASPR2 Abs while 43 patients were 'double negative' for these 2 Abs. Three 'double negative' patients had other neuronal surface Abs and were excluded from analysis. Compared to 'double negative' patients, a higher proportion of anti-LGI1/CASPR2 seropositive patients had complex partial seizures (5/7 vs 5/40; pâ¯=â¯.003), limbic encephalitis (4/7 vs 2/40; pâ¯=â¯.003), hippocampal imaging abnormalities (5/7 vs 3/39; pâ¯<â¯.001), temporal epileptiform activity/electrographic seizures (4/6 vs 4/27; pâ¯=â¯.020), tumours (3/7 vs 0/40; pâ¯=â¯.002), and received acute immunotherapy (5/7 vs 6/40; pâ¯=â¯.005) and maintenance immunotherapy (5/7 vs 4/40; pâ¯=â¯.001). Anti-LGI1/CASPR2 seropositive patients had higher anti-VGKC-complex Abs levels (median 2857 pM [range 933-6730] vs 165 pM [104-1065]; pâ¯<â¯.001). In contrast, a higher proportion of 'double negative' patients had non-specific behavioral disorders (20/40 vs 0/7; pâ¯=â¯.015), and 13 of 40 (32.5%) had alternative organic diagnoses. CONCLUSION: In anti-VGKC-complex seropositive patients, we identified features in patients with anti-LGI1/CASPR2 Abs distinct from 'double negative' patients, and found that 'double negative' patients were associated with non-specific clinical features and had a high rate of alternative diagnosis. These findings demonstrate the limited utility of anti-VGKC-complex Abs testing in suspected neurological autoimmunity.