Hashimoto's Thyroiditis Presents as an Acute Encephalopathy: A Case Report of Unusual Presentation.

Hashimoto's thyroiditis is the most common thyroid disorder in the United States. Hashimoto encephalopathy is a rare presentation of Hashimoto's thyroiditis that is frequently misdiagnosed. We present the case of a 71-year-old female who had normal mental status at baseline. She presented with acute alteration in mental status. Further evaluation with brain MRI showed a hyperintense signal in the bilateral centrum. Spinal fluid analysis revealed elevated protein. Thyroid peroxidase (TPO) antibody was elevated at 59.7 and TSH was elevated at 4.9. Her mental status improved dramatically after treatment with steroids and levothyroxine. This diagnosis should be suspected when the patient develops acute encephalopathy with positive serum thyroid antibody settings with a complete return to normal mental status after treatment with steroids.