Patty Duke, who won an Oscar as a teen for The Miracle Worker and maintained a long and successful career throughout her life, has died at the age of 69.

Duke's agent, Mitchell Stubbs, says the actress died early Tuesday morning of sepsis from a ruptured intestine. She died in Coeur D'Alene, Idaho, according to Teri Weigel, the publicist for her son, actor Sean Astin.

Duke found early success playing the young Keller first on Broadway, then in the acclaimed 1962 film version, both with Anne Bancroft as Helen's teacher, Annie Sullivan.

Then in 1963, she burst on the TV scene starring in a sitcom, The Patty Duke Show, which aired for three seasons. She played dual roles under an unconventional premise: as identical cousins living in Brooklyn, New York.

In 2015, she would play twin roles again: as a pair of grandmas on an episode of Liv and Maddie, a series on the Disney Channel. 

Obit Patty Duke

Actress Patty Duke is honoured with a star on the Hollywood Walk of Fame in Los Angeles on Aug. 17, 2004. (Damian Dovarganes/AP)

'I love you mom,' writes son Sean Astin

Astin posted a family statement on her death, accompanied by a photo of her carrying Astin as a toddler.

"This morning, our beloved wife, mother, grandmother, matriarch and the exquisite artist, humanitarian, and champion for mental health, Anna Patty Duke Pearce, closed her eyes, quieted her pain and ascended to a beautiful place. We celebrate the infinite love and compassion she shared through her work and throughout her life," read the statement.

"I love you mom," Astin wrote.

"We're so grateful to her for living a life that generates that amount of compassion and feeling in others," he told The Associated Press in reflecting on the outpouring of sentiment from fans at the news of her death.

She had "really, really suffered" with her illness, Astin added. From late last week until early Tuesday morning, he said, "was a really, really, really hard process. It was hard for her, it was hard for the people who love her to help her...."

'She was a joy,' says Glee actor

Actor Darren Criss worked with Duke on an episode of Glee. "Patty was wonderful," he told CBC News in an interview on Tuesday. "She was so open about her life and grateful to be around working, and to have had as long a run as she's had."

"She was a joy. That really breaks my heart. I'm sorry that she's left."

Darren Criss reacts to Patty Duke's death0:40

Mental health activist

Born Anna Marie Pearce in Queens, New York, on Dec. 14, 1946, Duke had a difficult childhood with abusive parents. By 8 years old she was largely under the control of husband-and-wife talent managers who soon found her work on soap operas and print advertising.

In the meantime, they supplied her with alcohol and prescription drugs, which accelerated the effects of her undiagnosed bipolar disorder.

In her 1988 memoir, Call Me Anna, Duke wrote of her condition and its diagnosis only six years earlier, and of the treatment that subsequently stabilized her life. The book became a 1990 TV film in which she starred, and she became an activist for mental health causes, helping to de-stigmatize bipolar disorder. 

Obit Patty Duke

In this April 8, 1963 file photo, Patty Duke, 16, accepts the Oscar as best supporting actress for her work in The Miracle Worker at the Academy Awards. (AP file photo)

With the end of The Patty Duke Show in 1966, which left her stereotyped as not one, but two squeaky-clean teenagers, Duke attempted to leap into adulthood in the 1967 melodrama Valley of the Dolls, in which she played a showbiz hopeful who falls prey to drug addiction, a broken marriage and shattered dreams.

The film, based on the best-selling Jacqueline Susann pulp novel, was critically slammed but a commercial smash.

Three-time Emmy winner

During her career she would win three Emmy Awards, for the TV film My Sweet Charlie, the miniseries Captains and the Kings and the 1979 TV remake of The Miracle Worker, in which Duke played Annie Sullivan and Little House on the Prairie actress Melissa Gilbert as Keller.

In the 1980s, she starred in a trio of short-lived sitcoms: It Takes TwoKaren's Song and Hail to the Chief, in which she was cast as the first female president of the United States.

She starred in several stage productions, including a return to Broadway in 2003 to play Aunt Eller in a revival of the musical Oklahoma!

Patty Duke

Patty Duke receives a kiss from sons, MacKenzie and Sean Astin following an unveiling ceremony honoring Duke with the 2,260th star on the Hollywood Walk of Fame in Los Angeles on Aug. 17, 2004. (Jim Ruymen JR/Reuters)

By then, she already had spent a dozen years living in Idaho with her fourth husband Michael Pearce, who survives her, seeking refuge from the clutter, noise and turmoil of big cities, and from the tumultuous life she had weathered in the past.

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. Not giving up."

with files from CBC News