Hashimoto's Encephalopathy With Progressive Cognitive Decline: A Rare Autoimmune Disorder in Central America.

Hashimoto's encephalopathy (HE) is a rare autoimmune disorder, typically associated with Hashimoto's thyroiditis, and often presents with rapidly progressive cognitive impairment, psychiatric symptoms, and neurological deficits. Since the first case reported, there have been relatively few reports of HE cases, and it remains rare in Central America. A 59-year-old male patient with a past medical history of hypertension (HTN) and type 2 diabetes mellitus (DM2) was hospitalized due to a one-month history of rapidly progressive cognitive impairment associated with behavioral changes and episodes of amnesia. It was not associated with motor or sensory deficits, seizures, or movement disorders. Given this presentation, alongside normal head CT findings and mild age-related brain atrophy on MRI, the initial diagnosis posed a challenge. Further investigations, including cerebrospinal fluid (CSF) analysis, autoimmune panels, and viral encephalitis testing, helped exclude other potential causes of encephalopathy. Notably, elevated anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) antibodies were detected, strongly suggesting HE. The patient responded favorably to immunosuppressive treatment with intravenous methylprednisolone and subsequent oral prednisone, leading to significant cognitive improvement and recovery of function. This case highlights the importance of considering HE in the differential diagnosis of rapidly progressive cognitive decline, especially when routine standard investigations do not reveal an alternative cause.