Patty Duke, the actress who won an Oscar at 16 for The Miracle Worker before starring as identical cousins in the beloved American sitcom The Patty Duke Show, died on Tuesday morning. She was 69.

The news was confirmed by Duke’s agent Mitchell Stubbs, who said that the actress died early Tuesday morning in Coeur D’Alene, Idaho, of sepsis from a ruptured intestine.

One of Duke’s three sons, the actor Sean Astin, further confirmed the death in a statement posted to Facebook, alongside a black-and-white photo of Duke holding Astin as an infant.

Astin’s statement, which begins with “I love you mom,” reads:

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.

Born Anna Marie Duke to a cashier and cabdriver in Queens, New York, Duke began acting as a child in commercials, print ads, and television soaps like The Brighter Day.

The eventual film and TV star first achieved fame onstage at the age of 12, appearing as Helen Keller opposite Anne Bancroft’s Annie Sullivan in the original Broadway production of William Gibson’s drama The Miracle Worker. When the production was adapted into a 1962 film, Duke won an Oscar for her role, becoming the youngest competitive Academy Award winner at the time.

The year after her Oscar win, Duke found mass fame with The Patty Duke Show, the ABC sitcom created for its teenage star. In over a hundred episodes, Duke starred as cousins Patty and Cathy—a premise that pushed special-effects boundaries for midcentury television and earned its star Golden Globe and Emmy nominations.

Despite her character’s sunny disposition on the sitcom, Duke was later diagnosed with bipolar disorder in 1982, and wrote about her struggles with mental illness, substance abuse, alcoholic parents, abusive managers, and a suicide attempt in her autobiography, Call Me Anna.

In spite of those demons, Duke triumphed as a tireless advocate for mental-health programs, an actor in her later years, and a mother of three sons—two of whom, Sean and Mackenzie Astin, have also become actors.

In her memoir, Duke wrote, “I’ve survived. I’ve beaten my own bad system and on some days, on most days, that feels like a miracle.”

Duke is survived by both Sean and Mackenzie as well as her husband, Michael Pearce, and their son Kevin Pearce.