A Rare Case of Hashimoto's Encephalopathy With Mosaic Turner Syndrome.

Mosaicism in Turner syndrome (TS) is a 20%-30% occurrence, with 45, X plus at least another cell line. The haploinsufficiency of the X chromosome is usually responsible for the higher risk of autoimmunity in TS, exhibiting mainly as thyroiditis, type 1 diabetes, etc. Though Hashimoto's thyroiditis is commonly seen in patients with TS, the concurrence of encephalopathy in these patients is significantly rare and has not been reported. We present a case of a young female with mosaic TS who presented with altered mental status. The initial workup was negative for stroke and pulmonary embolism and cerebrospinal fluid (CSF) analysis did not show any infectious etiology. Thyroid peroxidase (TPO) antibodies (Abs) and thyroglobulin Abs were elevated. As the patient's mental status deteriorated, there was a concern for Hashimoto's encephalopathy (HE), hence the patient was started on high-dose IV steroids. Within 24 hours, the patient responded to the IV steroids and an improvement in mentation was noted. HE is a rare immune-mediated disorder, characterized by impaired brain function. The onset of which can be rapid or slowly developing over the course of many years but responds effectively to steroids. Turner syndrome is associated with a high incidence of autoimmune disorders, thus in the setting of a negative workup for more obvious causes, HE should be a consideration when encountered in a clinical scenario.