Fingerprint patterns may provide a clue to Alzheimer's disease.

A study of 100 people -- 50 with Alzheimer's, 50 without -- showed that the ones with Alzheimer's had a "significntly increased frequency" of a certain kind of fingerprint pattern

A similar finding had been made in Down's syndrome patients, lending support to theories that the two afflictions are genetically related.

"It points in the direction of chromosome 21," said Dr. Herman J. Weinreb of New York University. "We know that fingerprints come from genetic forces. So there is some genetic element to this." Down's syndrome is known to be caused by an extra 21st chromosome -- a condition that hasn't been found in Alzheimer's patients.

Alzheimer's is an irreversible deterioration of the brain that usually strikes old people.

People with Down's syndrome, a form of mental retardation, develop Alzheimer's by age 40, he said. He reported his fingerprint findings in the January issue of the Archives of Neurology.

Fingerprints come in four basic patterns: arches, which reach across each finger; whorls, which are closed circles; radial loops, which open toward the thumb; and ulnar loops, which open toward the pinky. While most people have ulnar loops on six fingers, people with Down's syndrome or Alzheimer's have the pattern on eight to 10, Weinreb said.

But he warned that the presence of the ulnar loop pattern doesn't mean someone will develop Alzheimer's. "It's only a statistical association," he said. "It's not a parlor diagnostic test where you can look at your fingertips and predict the future."