Fatal familial insomnia is a rare prion disease that interferes with sleep and leads to deterioration of mental and motor functions. Death occurs within a few months to a few years.

Fatal insomnia includes an inherited or familial form, called fatal familial insomnia, due to a specific mutation in the PrP^c gene. The disease can also occur spontaneously, without a genetic mutation. This form is called sporadic fatal insomnia. Fatal familial insomnia and sporadic fatal insomnia differ from other prion diseases because they affect predominantly one area of the brain, the thalamus, which influences sleep.

The disease usually begins between the ages of 40 and 60 but may begin in a person's late 30s. At first, people may have minor difficulties falling asleep and occasional muscle twitching, spasms, and stiffness. Eventually, they cannot sleep. Occasionally, the sleep signs are difficult to detect. Other changes include a rapid heart rate and dementia. Death usually occurs about 7 to 36 months after symptoms begin.

The diagnosis is suggested by typical symptoms and a family history of the disease and can be confirmed by genetic testing. No treatment is available.

Last full review/revision January 2007 by Pierluigi Gambetti, MD