Steroid-Responsive Encephalopathy associated with Autoimmune Thyroiditis (SREAT) presenting as malignant excited catatonia: A novel clinical presentation

Hashimoto Encephalopathy, more accurately known as Steroid Responsive Encephalopathy associated with Autoimmune Thyroiditis (SREAT), is an exceedingly rare and often controversial diagnosis that, when present, manifests as encephalopathy with a variety of other potential symptoms in the setting of elevated antithyroid peroxidase antibody and/or antithyroglobulin antibody. Its manifestations can include encephalopathy, seizures, myoclonus, hallucinations, stroke-like findings, and more. We present the case of a 39-year-old transgender man with autistic spectrum disorder and depression, initially presumed to be in acute psychiatric decompensation, later found to have elevated levels of anti-thyroid peroxidase antibodies, who responded well to plasma exchange (PLEX) and rituximab. On initial psychiatric admission, the patient had symptoms of suicidal ideation, confusion, and agitation. He showed little improvement on medications such as quetiapine, olanzapine, valproate, and bupropion. Due to worsening agitation and cognitive impairment, he required further medical and neurological evaluation. He later had an episode deemed to be a likely seizure. This workup included electroencephalogram (EEG), MRI Brain, and lumbar puncture, yet all were unremarkable. Laboratory values were notable for elevated anti-thyroid peroxidase (TPO) antibodies of 661 U/mL. The patient received intravenous high-dose steroids with transient improvement. He eventually responded dramatically to plasmapheresis. At his post-discharge follow up, he had returned to his cognitive baseline. He successfully resumed his job and has since remained at his functional baseline. This case is the first to our knowledge to characterize a novel presentation of SREAT mimicking malignant excited catatonia. In such cases, if initial response to glucocorticoid treatment is equivocal, plasma exchange may be an effective treatment option.