Steroid responsive encephalopathy associated with autoimmune thyroiditis (SREAT) presenting as major depression

Background: Hashimoto's encephalopathy is a neuropsychiatric disease with symptoms of cognitive impairment, stroke-like episodes, seizures, and psychotic or affective symptoms associated with autoimmune thyroiditis and excellent steroid responsiveness; therefore, it is also called "steroid responsive encephalopathy associated with autoimmune thyroiditis" (SREAT). Case presentation: We present the case of a 50-year-old woman who developed a first-onset depressive syndrome with predominant cognitive impairment and inability to work. Antidepressive treatment and cognitive behavioral therapy over two years were unsuccessful. Neurological examination was unremarkable. Serum analysis showed increased thyroid peroxidase and thyroglobulin antibodies. Cerebrospinal fluid protein and albumin quotient were increased. Magnetic resonance imaging depicted unspecific, supratentorial white matter lesions and frontal accentuated brain atrophy. Electroencephalography was normal. Neuropsychological testing for attentional performance was below average. High-dose intravenous treatment with methylprednisolone over 5 days and oral dose reduction over 3 weeks led to the sustained improvement of clinical symptoms. Following discharge from the hospital, the patient returned to work, and 6.5 months after the start of therapy, no neuropsychological deficit remained. Conclusion: This case report illustrates that SREAT might present with purely depressive symptoms, thus mimicking classical major depression. In such cases, corticosteroid therapy may be an effective treatment option.