Fatal insomnia is a rare disorder that results in trouble sleeping. The problems sleeping typically start out gradually and worsen over time. Other symptoms may include speech problems, coordination problems, and dementia. It results in death within a few months to a few years.

It is a prion disease of the brain. It is usually caused by a mutation to the protein PrPC. It has two forms: fatal familial insomnia (FFI), which is autosomal dominant and sporadic fatal insomnia (sFI) which is due to a noninherited mutation. Diagnosis is based on a sleep study, PET scan, and genetic testing.

Fatal insomnia has no known cure and involves progressively worsening insomnia, which leads to hallucinations, delirium, confusional states like that of dementia, and eventually death. The average survival time from onset of symptoms is 18 months. The first recorded case was an Italian man, who died in Venice in 1765.

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