Medicine

Alzheimer's disease, among the most horrifying to strike the elderly, is also one of the most mysterious. Now scientists have found a small but tantalizing clue to its workings. Dr. Dennis J. Selkoe, co-director of the Center for Neurologic Diseases at Boston's Brigham and Women's Hospital, led a team of researchers that detected deposits of beta amyloid protein, long associated with Alzheimer's, in the skin, blood vessels and intestines of patients with the disorder. Previously the beta amyloid had been found only in the brains of Alzheimer's victims. The study, reported in last week's Nature, suggests that Alzheimer's may not begin in the brain, as has generally been assumed. This new knowledge could lead to a practical skin test for detecting the disease and may eventually help scientists learn how to prevent it.

The most common cause of dementia in the elderly, Alzheimer's killed some 100,000 Americans last year and afflicts 2.5 million with what has been called the death of the mind. Symptoms include severe loss of memory and personality changes that range from angry outbursts to withdrawal and depression. Diagnosis -- at best tentative -- has been possible only through a process of eliminating other brain ailments that could cause similar symptoms.

The brains of victims characteristically contain plaques that include the beta amyloid, but its presence can only be confirmed after death. Whether it helps cause the brain degeneration or is a by-product is not clear. But if the beta amyloid is the cause, then the Boston research could represent a turning point. The study suggests that the suspect chemical may be produced in one or more tissues outside the brain, circulate in the bloodstream and enter various other tissues. But damage seems to occur only when the beta amyloid is deposited in certain regions of the brain important to memory and intellect. If that is true, then a way might be found to block the delivery of the protein to the brain. That could slow down -- or even halt -- Alzheimer's.