TEXT C Imagine what a nightmare it would be to never have a nightmare, to never again have a dream, to be banished forever from the topsy——turvy realm of sleep. Just imagine what it would be like one day to wake up and never fall asleep again, to be tortured in a twilight world of perpetual insomnia, lying in bed, exhausted but with eyes wide open, listening to the groans and whispers of the night——sleepless, until death mercifully claims you. It's not a lost Gothic chiller from Edgar Allen Poe but a very real, and very rare, disease called "fatal insomnia." We might have never heard of it without the medical detective work of an Italian family, which, it turns out, was stalked for centuries by a terrifying fate. As clinical tapes show, insomnia has become an all-too waking reality for this family. But as difficult as their experience has been, it has pushed the outer boundaries of what we know about sleep and expanded our understanding of human disease itself. This family's illness might lead to breakthroughs in curing diseases like Alzheimer's and Parkinson's. Dr. Ignazio Roiter: "The first person to fall ill was my wife's aunt. They said she was de- pressed." Dr. Ignazio Roiter is a country doctor. His wife, Elisabetta, is a descendant of a prominent Italian family with roots in Venice since the 1600s. Roiter's medical training hadn't prepared him for the sad and puzzling ailment that was suddenly overtaking Elizabetta's aunt, a woman in her 40s. Dr. Roiter: "She appeared to be sleeping all the time, but then she claimed she had insomnia. The doctors were confused." Sleeping pills were useless. The two could only watch in horror as the aunt's health deteriorated. After a few months she could no longer walk, even speaking was an effort. Dr. Roiter: "The disease progresses very rapidly. Death comes suddenly." The aunt was dead one year after the onset of her mysterious sleepless condition. Then a year later, in 1979, it struck again. A second aunt became suddenly sleepless.