Two PerPLEXing Cases of Hashimoto's Encephalopathy Unresponsive to Steroid and Intravenous Immunoglobulin Therapy.

Hashimoto's encephalopathy is a nebulous entity over which much controversy exists. Often referred to as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), it describes a myriad of neurological sequelae that typically are observed to occur in patients with the presence of thyroid antibodies. We aim to raise clinical awareness of this seldom diagnosed entity as a potential etiology for altered mental status in patients who present with supporting clinical features and elevated thyroid antibodies. While steroid responsiveness is deemed a typical presenting feature of this medical condition, our cases aim to describe two cases that required escalation of therapy to intravenous immunoglobulins, and ultimately, plasmapheresis therapy for improvement in their clinical status. Our patients had a dramatic improvement in their mentation within three to four sessions of plasmapheresis, improving rapidly toward their baseline. Such a dramatic improvement, coupled with the corresponding reduction in their thyroid antibody titer supports the diagnosis of Hashimoto's encephalopathy and highlights the importance of having a low clinical threshold for the diagnosis of this entity in patients who, despite extensive evaluation, reveal no apparent cause for their altered mental status.