lecules are folded into the correct shape, prions are benign, though no one knows their function.Folded the wrong way, prions induce other proteins to mimic them. The misfolded prions then accumulate in parts of the brain, causing the tissue to break down and become full of holes, like a sponge.Different prion diseases attack different parts of the brain, causing characteristic types of dementia and death.Some are infectious, like mad cow disease in cattle and scrapie in sheep and goats. In humans, prion diseases are either inherited, caught from eating contaminated meat, or spontaneous.Researchers have previously identified an inherited prion disorder whose main symptom is sleeplessness, called fatal familial insomnia.In a case outlined in Thursday's New England Journal of Medicine, a 44-year-old patient had all the symptoms of the inherited disease, including prions with the same ''signature,'' but did not have the inherited mutation. The case was reported by Dr. James Mastrianni, a neurologist at the University of Chicago.The spontaneous, or sporadic, versions of the prion diseases are rare, but more common than their inherited counterparts.Prions are still controversial. Some researchers believe it is impossible for proteins to replicate and cause disease, since they do not contain genetic material. These researchers believe the diseases are instead caused by as-yet-undiscovered viruses.However, the new studies add to evidence the infection is caused by the abnormal shape of the prions, not another agent, Drs. Pierluigi Gambetti and Piero Parchi of Case Western Reserve University said in an accompanying editorial.Gambetti and Parchi have described five similar cases of non-inherited fatal insomnia in a study scheduled to appear in the journal Neurology....
