Seropositive autoimmune encephalitis is a heterogeneous and rapidly expanding diagnostic category with variable presentations and treatment responsivity.
To determine the distribution, clinical characteristics, responses to treatment and clinical outcomes for real-world cases of confirmed seropositive autoimmune encephalitis.
Patients within a single, tertiary medical center identified to have positive blood or CSF autoantibodies on panels sent to Mayo Laboratories between January 2010 and December 2019 were identified and retrospective chart reviews were performed. Patient with low antibody titers and clinical features not suggestive of an autoimmune syndrome were excluded.
1858 patients were tested for autoimmune encephalitis antibody panel. Two hundred nineteen (11.79%) had positive autoantibodies but only 42 cases fulfilled the inclusion criteria. The mean age of the patients was 53.4 (± 21.4) with 71.4% female predominance. The majority of the patients presented with altered mental status (n=15, 35.7%) or new onset seizure (n=13, 30.9%).The most common autoantibodies detected were anti NMDA (n=12, 28.6%) followed by anti LGI (n=11, 26.2%) and anti-neuronal nuclear antibody (ANNA, or anti-Hu, n=9, 21.4%). The most common treatments used were steroids (n=37, 88.1%) and IVIg (n=31, 73.8%). Rituximab was the most common second line treatment (n=20, 47.6%). The worst clinical outcomes were seen with ANNA-associated syndromes; these patients had a mean modified Rankin score of 5.8(± 0.3). Six of these patients had a small cell lung cancer. Patients with NMDA and LGI autoantibodies had a better response to treatment with mean mRS of 1.8 (± 1.03) and 1.5 (± 1.36) respectively.
Anti-NMDA and LGI were the most commonly detected autoantibodies in our cohort and also had the best clinical outcomes. Patient with ANNA had the worst clinical outcomes and small cell lung cancer was the most common associated malignancy.