To elucidate the clinical profile of sporadic fatal insomnia (sFI), assess the similarities and differences between sFI and fatal familial insomnia (FFI), and evaluate the influence of ethnicity on the phenotype of sFI patients.
The data of sFI and FFI patients was retrieved from our case series and through literature review. The clinical and diagnostic features of sFI and FFI were compared, as were the phenotypes of Asian and Caucasian sFI patients.
We identified 44 sFI and 157 FFI cases. The prevalence of sleep-related, neuropsychiatric and autonomic symptoms among the sFI patients were 65.9%, 100.0% and 43.2% respectively. Compared to FFI, sFI exhibited longer disease duration and a higher proportion of neuropsychiatric symptoms, while FFI was characterized by a higher incidence of sleep-related and autonomic symptoms in the early stages of the disease or throughout its course. In addition, a higher proportion of the sFI patients showed hyperintensity on MRI and PSWCs on EEG compared to the FFI patients, especially those presenting with pathological changes associated with MM2-cortical type sCJD. The Asian sFI patients had a higher proportion of males and positivity for CSF 14-3-3 protein, and fewer sleep-related symptoms compared to Caucasian sFI patients. The age of onset and duration of sFI differed between ethnic groups, but failed to reach statistical significance.
Despite its similarities to FFI, sFI is characterized by longer disease duration, higher proportion of neuropsychiatric symptoms and hyperintensity on MRI, along with differences in the clinical characteristics based on ethnicity.

This article is protected by copyright. All rights reserved.