Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT) is a rare condition defined by encephalopathy with acute or subacute onset, the presence of serum anti-thyroid antibodies, and reasonable exclusion of alternative causes. Despite strong response towards corticosteroid treatment, some patients exhibit a chronic-relapsing course and require long-term immunosuppression. Markers for early identification of those patients are still absent.
We retrospectively evaluated a cohort of 22 SREAT patients treated in our Hospital since January 2014.
14 patients with a monophasic disease course and 8 patients with multiple relapses were identified. Baseline characteristics as well as routine CSF parameters did not distinguish between those patients. Flow cytometry following initial relapse therapy displayed a treatment-resistant sequestration of activated CD4+ T cells in patients with a relapsing disease course whereas other lymphocyte subsets showed uniform changes. Such changes were also present in long-term follow-up CSF examination.
Our findings indicate a potential biomarker for risk stratification in SREAT patients. Currently, it remains unclear whether the observed two phenotypes are different spectra of SREAT or represent separate diseases in terms of pathophysiology.

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