Fatal Familial Insomnia

Fatal familial insomnia (FFI) is a very 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 is an incurable disease, involving progressively worsening insomnia, which leads to hallucinations, delirium, and confusional states like that of dementia.[1] The average survival span for patients diagnosed with FFI is 18 months.[2]

The mutated protein, called PrPSc, has been found in just 40 families worldwide, affecting about 100 people; if only one parent has the gene, the offspring have a 50% chance of inheriting it and developing the disease. The first recorded victim was an Italian man, deceased in Venice in the year 1765. [3]

http://en.wikipedia.org/wiki/Fatal_familial_insomnia