One unkind form, known as fatal familial insomnia, has been passed down in an Italian family for several generations.

Others, like Creutzfeldt-Jakob disease and fatal familial insomnia, are exceedingly rare diseases of humans.

In fact, the cause of death was always the same: fatal familial insomnia, a genetic disease that was not formally identified until 1986.

Their hunch that mad cow disease and fatal familial insomnia were somehow connected would turn out to be right.

Many questions about fatal familial insomnia remain.

Even though the likelihood of having fatal familial insomnia is one in 33 million, in her family, it is one in two.

Complete absence of sleep over long periods is impossible for humans to achieve (unless they suffer from fatal familial insomnia); brief microsleeps cannot be avoided.

A rare genetic condition can cause a prion-based, permanent and eventually fatal form of insomnia called fatal familial insomnia.

In fatal familial insomnia, the prion chains form plaque in the thalamus, which regulates sleep and other functions.

A very rare disease called fatal familial insomnia prevents some people from falling asleep.