NIH

Zebra of the Week: Fatal familial insomnia

June 30, 2025

Fatal familial insomnia (FFI) is a rare, autosomal dominant prion disease primarily affecting the thalamus, leading to progressive disruption of the sleep-wake cycle. Clinical manifestations typically begin with intractable insomnia and evolve to include neuropsychiatric disturbances, autonomic dysfunction (e.g., hyperhidrosis, hypertension, thermoregulatory instability), weight loss, and cerebellar signs such as ataxia. Symptomatology is relentlessly progressive.

The condition is most often associated with a pathogenic variant in the PRNP gene. Diagnostic evaluation includes clinical assessment, polysomnography, neuroimaging (often showing thalamic hypometabolism on PET), and confirmatory genetic testing.

Source:

(Accessed 2025, June 27). NIH [Genetic and Rare Diseases Information Center]. Fatal familial insomnia. https://rarediseases.info.nih.gov/diseases/6429/fatal-familial-insomnia