Fatal familial insomnia
(FFI) is an extremely rare autosomal dominant inherited prion disease
of the brain
. It is almost always caused by a mutation
to the protein PrPC
, but can also develop spontaneously in patients with a non-inherited mutation variant called sporadic fatal insomnia
(sFI). FFI has no known cure and involves progressively worsening insomnia
, which leads to hallucinations, delirium, and confusional states like that of dementia. The average survival span for patients diagnosed with FFI after the onset of symptoms is 18 months.