Hashimoto's encephalopathy: a rare cause of delirium.

Cognitive impairment is a frequent presentation of patients who come to the hospital. We report a case of a patient who presents with a common symptom, however, with a rare disease. This is an 84-year-old woman with a history of hypertension and atrial fibrillation who was reported to have confusion of 3 weeks. Investigations, including a complete blood count, MRI imaging of the brain, cerebrospinal fluid analysis and paraneoplastic screen, were all negative. Of note, thyroid peroxidase antibody was elevated. She did not have a history of thyroid disease. Following this, an assessment of Hashimoto encephalopathy was made. She was started on steroids and she showed remarkable recovery within 2 months, therefore, confirming the diagnosis. This case report emphasises the need to consider Hashimoto's encephalopathy as a differential for delirium especially when other common aetiologies have been ruled out.