The TIME 100

People sometimes veer into their own legacy after being blindsided by fate. Michael J. Fox is one of those people. Diagnosed with young-onset Parkinson's disease in 1991 at age 30, he spent the next seven years working as an actor and keeping his condition secret from everyone except those closest to him.

He could have been forgiven for never disclosing it or for hiding once the symptoms became obvious. Instead, in 1998 he told the world. Then he stepped onto the front lines of the effort to find a cure. Stem-cell treatment, he learned, has the potential not only to cure the disease that has afflicted him but also to treat other tragic diseases, such as Alzheimer's and ALS. Testifying on Capitol Hill in 1999, the effects of Parkinson's clearly visible, he spoke about others with the disease—people who are too embarrassed to leave their homes or who have found themselves suddenly helpless, stranded in bathtubs or beds, unable to move.

He could certainly have been forgiven for lashing back at Rush Limbaugh, who, during the 2006 campaign, accused Fox of faking his symptoms in a TV ad endorsing Claire McCaskill, Missouri's Democratic candidate for the U.S. Senate—and, in a reprehensible demonstration of cruelty, imitated him. But Fox, 45, rose above it with a gallantry of spirit that also cannot be faked. He is to be celebrated for his work, his kindness, his humor under duress, and for a noble heart.

Davis' father President Ronald Reagan had Alzheimer's disease