# Creutzfeldt-Jakob disease mimicking Hashimoto’s encephalopathy: steroid response followed by decline

## TL;DR

A case of Creutzfeldt-Jakob disease was initially mistaken for Hashimoto’s encephalopathy due to similar symptoms and a brief response to steroids.

## Contribution

The paper highlights the diagnostic challenge of CJD mimicking autoimmune encephalopathy and emphasizes the importance of early confirmatory testing.

## Key findings

- Short-term steroid treatment led to temporary improvement followed by rapid decline in a CJD patient.
- MRI and EEG findings evolved over time, aiding in the diagnosis of prion disease.
- CJD can resemble Hashimoto’s encephalopathy, even with elevated thyroid antibodies.

## Abstract

The diagnosis of Creutzfeldt–Jakob disease (CJD) is particularly challenging because its heterogeneous clinical presentations mimic other rapidly progressive dementias and neurodegenerative disorders (e.g., Hashimoto’s encephalopathy, autoimmune encephalitis, atypical Alzheimer’s disease). Diffusion-weighted imaging (DWI) is the most sensitive neuroimaging sequence for diagnosing CJD. However, early magnetic resonance imaging (MRI) findings may be subtle or evolving, and autoimmune etiologies often remain in the differential. Therefore, empiric corticosteroids are reserved for cases in which an autoimmune etiology is under consideration while definitive tests are pending. A 67-year-old woman presented with rapidly progressive cognitive decline, ataxia, and visual symptoms. Short-course glucocorticoids produced transient improvement for three days, followed by rapid deterioration within a week. Serial MRI evolved from cortical ribboning to basal ganglia involvement. Electroencephalogram (EEG) showed non-convulsive status epilepticus that responded to diazepam and valproate. Cerebrospinal fluid (CSF) 14-3-3 protein (14-3-3) and RT-QuIC were positive, confirming prion disease. CJD can present with features resembling HE, and brief improvement after a short course of glucocorticoids, even in the presence of markedly elevated thyroid antibodies, does not exclude CJD. To avoid diagnostic delay, obtain CSF RT-QuIC and 14-3-3 at presentation before or in parallel with glucocorticoids, and use serial MRI and EEG to arbitrate.