Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis: A Case Fulfilling Definite Graus Criteria

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), also known as Hashimoto encephalopathy, is a rare immune-mediated neurological syndrome with an incidence of 2.1 per 100,000 and a 4:1 female predominance. Neurological manifestations are independent of thyroid status, occurring in 30–40% of euthyroid patients, and include cognitive impairment, confusion, seizures, and psychiatric symptoms. Diagnosis is challenging in the elderly, where symptoms overlap with dementia or delirium, with only 51 reported cases in patients aged ≥65 years. We describe a 70-year-old woman with autoimmune hypothyroidism and levothyroxine nonadherence who presented with progressive weakness, melena, dyspnea, and altered mental status complicated by obstructive uropathy, gastrointestinal bleeding, hypocalcemia, and severe hypothyroidism. Despite normalization of metabolic parameters and thyroid function, profound encephalopathy with fluctuating alertness, psychomotor slowing, memory impairment, psychosis, and a seizure-like episode persisted. Workup revealed elevated anti-thyroid antibodies, positive ANA, inflammatory CSF, diffuse EEG slowing, and low-titer GAD65 antibodies. High-dose prednisone led to dramatic improvement within 48 hours, fulfilling adapted Graus criteria for definite SREAT. This case distinguishes SREAT from myxedema coma by the temporal dissociation between thyroid normalization and steroid response, emphasizes avoiding overinterpretation of low-titer GAD65 antibodies, and highlights CSF findings as supportive evidence. Early recognition is crucial in elderly patients with refractory encephalopathy and autoimmune thyroiditis.