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 it can also develop spontaneously in patients without the inherited mutation in a variant called sporadic fatal insomnia (SFI). 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 disease's genesis and the patient's progression into complete sleeplessness is untreatable and ultimately fatal.
The age of onset is variable, ranging from 35 to 60, with an average of 50. However the disease tends to prominently occur in later years, primarily following childbirth. The disease can be detected prior to onset by genetic testing. Death usually occurs between 7 and 36 months from onset. The presentation of the disease varies considerably from person to person, even among patients from within the same family.
The disease has four stages, taking 7 to 18 months to run its course:
Other symptoms include profuse sweating, pinprick pupils, the sudden entrance into menopause for women and impotence for men, neck stiffness, and elevation of blood pressure and heart rate. Constipation is common as well.
There is no cure or treatment for FFI. Gene therapy is so far unsuccessful. While it is not currently possible to reverse the underlying illness, there is some evidence that treatments that focus upon the symptoms can improve quality of life. 
Recently, a mouse model was made for FFI. These mice express a humanized version of the PrP protein that also contains the D178N FFI mutation.  These mice appear to have progressively fewer and shorter periods of uninterrupted sleep, damage in the thalamus, and early deaths, similar to people with FFI.
There are other diseases involving the mammalian prion. Some are transmissible (TSEs) such as kuru, bovine spongiform encephalopathy (BSE, also known as "mad cow disease") in cows, and chronic wasting disease in American deer and American elk in some areas of the United States and Canada, as well as Creutzfeldt-Jakob disease (CJD). These are generally not considered to be transmissible except by direct contact with infected tissue, such as from eating infected tissue, transfusion or transplantation.
Full article ▸