Hepatitis B is a similar liver disease that can range from a mild illness to a serious, chronic condition.

CNN: Dozens of Okla. dentist's patients positive for hepatitis

Rothberg's 14-year-old daughter, the oldest of his five kids, has a mild form of an inherited disease called tuberous sclerosis complex, a relatively rare disorder (50, 000 or so Americans have it) that can cause benign tumors in the heart, kidney, skin, lungs, eyes and brain, where seizures can occur.

FORBES: Companies, People, Ideas

And pre-specified secondary subgroup analyses of pooled data across both studies showed a statistically significant slowing of cognitive decline in patients with mild disease, but not in those with moderate disease.

FORBES: Lilly's Big Alzheimer's Bet: Will It Pay Off?

Meanwhile, the Allon Therapeutics drug helped improve some measures of short-term memory in patients with mild cognitive impairment, a condition that often leads to Alzheimer's disease.

FORBES: Alzheimer's Drug Showdown

When it learned of these results Myriad switched its focus from cancer to Alzheimer's disease and began a trial of 210 men and women with mild to moderate Alzheimer's symptoms.

FORBES: Magazine Article

Prof Robert Modlin, a dermatology and microbiology expert at the University of California, Los Angeles, said the study raises the possibility that a decrease or increase of one of these two proteins could shift the balance from mild to more serious disease.

BBC: 'Wrong' immune response aids TB

He adds he has heard from some people who have used the product even with mild cognitive symptoms but no diagnosis, or even a few with no symptoms but family histories of Alzheimer's disease.

WSJ: 'Medical Foods' and Supplements for Brain Health Advance