Fatal familial insomnia

Most of you have heard about 'mad cow' disease, a fast-spreading and disastrous affliction. It was passed on animal to animal - to person - by the ingestion of meat with disease-causing proteins. These proteins were named 'prions'. Prions have mutations in them that cause them to misfold and accumulate en masse within the brain. Even injecting the fluid of an prion-infected animal into a healthy animal would make the latter animal sick.

There are other prion diseases out there that you may not be familiar with. One is related to sleep, called fatal familial insomnia (FFI). A person with FFI, as the name suggests, is completely unable to sleep. One common sign of disease initiation is constricted pupils. This is followed by the inability to sleep, severe hallucinations and paranoia, weight loss, dementia and certain death. The time course from FFI onset to death is typically about a year.

Fortunately, the disease is extremely rare. It occurs in about 40 families around the world, and is only passed on through (autosomal dominant) inheritance. (In each of these families, however, there were distinct Patient Zeros in whom the mutation first arose.) The age of disease onset is typically later in life, so unless one undergoes a DNA test, he (or she) will not know if his children can inherit the gene mutation. This is the cruel trick of the prion; most other fatal genetic mutations don't get past the womb.

Although it is known that this prion also causes plaques in the brain, it is not known why it specifically prevents sleep. And so far, no attempted treatments have shown any promise.

Here's a clip from ABC about FFI:



I also highly recommend reading The Family That Couldn't Sleep about the history of the earliest known cases of FFI.