As a child star Duke was famous for her portrayal of Helen Keller in the 1962 film The Miracle Worker. She first played the role on Broadway in 1959, with Anne Bancroft as Keller's teacher Anne Sullivan; the film version won Oscars for both Duke and Bancroft. The Patty Duke Show, in which she played identical cousins from different backgrounds, was a hit from 1963-66. She continued her acting career into adulthood, making something of a specialty of TV movies. She was married to the actor John Astin (famous for playing Gomez on TV's The Addams Family) from 1972-85; their sons Sean and Mackenzie also are actors. 

In the early 1980s Duke was diagnosed with manic depression; in 1992 she published a book about the disease, A Brilliant Madness. 

Credit: who2.com