Steroid-responsive Encephalopathy Associated with Autoimmune Thyroiditis: Clinical Presentation and Misdiagnosis (1900)

Objective: To describe the spectrum of cases referred to Autoimmune Neurology at Mayo Clinic with suspected steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT). Background: SREAT, also known as Hashimoto encephalopathy, is defined by subacute onset encephalopathy, with thyroid antibodies, and objective neurological improvement after immunotherapy, in the absence of other neural autoantibodies. Design/Methods: Retrospective review of clinical, laboratory and radiologic findings in patients referred with suspected SREAT from 2006 to 2019. Results: 143 patients were included in the study. 71% were female. Median age was 45 years. 68% had history of thyroid disease. 80% had received immunotherapy. After our evaluation, 38 patients (27%) were diagnosed with autoimmune encephalopathy. 26% of them had neural autoantibodies, including VGKC (n=3), GAD65 (n=3), VGCC (n=3), acetylcholine receptors (n=2), AMPAR (n=1), unclassified (n=1). 105 patients (73%) were given an alternative diagnosis including subjective cognitive complaints (n=26), conversion (n=20), and neurodegenerative (n=16) disorders amongst others. TPO antibody titer was not significantly different between the groups (median 168.5IU/mL). Patients with autoimmune encephalopathy were more likely to present with subacute symptoms (p Conclusions: A significant number of patients with suspected SREAT had an alternative non-immune mediated disorder. SREAT diagnosis should not be made without objective evidence of encephalopathy, and should only be considered after exclusion of other causes. TPO antibody prevalence is high, and only reflects a predisposition to autoimmunity. It may also be detected in coexistence with other neural antibodies. Documentation of objective abnormalities at baseline and post-treatment comparison is essential to avoid misdiagnosis. Disclosure: Dr. Valencia Sanchez has nothing to disclose. Dr. Pittock has received personal compensation from Alexion, Grifols, Euroimmun, MedImmune/Viela Bio Dr. Pittock has received research support from Alexion, Grifols, Euroimmun, MedImmune/Viela BioDr. Dubey has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Consulted for UCB and Astellas. All compensation for consulting activities is paid directly to Mayo Clinic.. Dr. Dubey has received research support from Research support from Grifols and Center of Multiple Sclerosis and Autoimmune Neurology, Center for Clinical and Translational Science. Patent pending for KLHL11 as a marker of neurological autoimmunity.. Dr. Flanagan has received research support from Medimmune/Viela Bio.Dr. Lopez has nothing to disclose. Dr. Zalewski has nothing to disclose. Dr. Zekeridou has received research support from patent pending on PDE10A-IgG as a biomarker of paraneoplastic autoimmunity. Dr. McKeon has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Grifols, Medimmune, and Euroimmun. Dr. McKeon has received royalty, license fees, or contractual rights payments from Pending patents: MAP1B, Kelch-like-protein 11, GFAP and MAP1B. Dr. McKeon has received research support from Medimmune, Euroimmun but has not received personal compensation..