Duke was diagnosed with bipolar disorder in 1982 and became a devoted advocate to education of mental health issues.
In describing the role of Aunt Eller, and perhaps herself, to The Associated Press, she said, "This is a woman who has had strife in life, made her peace with some of it and has come to the point of acceptance".
"Anna (her given name) fought for civil rights, gay rights and the rights of working actors to name just a few".
Then in 1963, Duke burst on the TV scene starring in her own sitcom, "The Patty Duke Show", which aired for three seasons. "What I don't like is for people to believe I chose to do destructive things".
Duke won an Academy Award in 1963 for her role in "The Miracle Worker" about Helen Keller.
Duke continued to find success on the small screen, earning three Emmy awards, including wins for Captains and Kings and My Sweet Charlie.
Glee star Chris Colfer, who shared scenes with Duke during her stint on the show, paid tribute to the late star hailing her as a "wonderful and talented person" and someone he loved to work with.
In addition to being a stage, film and television actress, Duke was a mental health advocate. But she's most fondly remembered for playing twin cousins on "The Patty Duke Show" also in the early 60s.
Duke went on to star in films as well, including 'Valley of the Dolls'. She revisited the material in 1979 for a TV version of the play, for which she won an Emmy playing Keller's teacher - the role originally played on Broadway by Anne Bancroft.
Duke would not sustain stardom into adulthood although she worked regularly on television and during the mid-1980's served as President of the Screen Actors Guild.
Duke's son Sean Astin said the family is "relieved" because Duke was in a lot of pain and the process took a long time to play out. We (are) having a very happy and quiet day. Patty's other son, MacKenzie Astin, is also a well known actor.
Michael Pearce was the actress' fourth husband.