Patty Duke, the actress who rocketed to fame playing Helen Keller in the 1959 Broadway drama The Miracle Worker and then the film version in 1962, died March 29 in Coeur D’Alene, ID. The cause was sepsis from a ruptured intenstine. She was 69.

Few breakout successes by child stars were as sudden, assured and sustained as that of Ms. Duke. William Gibson’s earnest play, adapted from his own teleplay written for Playhouse 90, told the story of the relationship between Keller, who was famously born deaf and blind and almost completely lacking in language, and the teacher Anne Sullivan’s fierce determination to bring the child into the greater sensory world.

Born December 14, 1946, in Elmhurst, Queens, Anne Marie Duke began acting early on, taking parts in commercials and soap operas. She was the product of unhappy parentage; her father was an alcoholic and her mother prone to depression and violence. By the time she was eight, she was in the custody of talent managers John and Ethel Ross, who changed her name and often exploited her.

Her intense, primal performance in The Miracle Worker brought her the attention of theatre critics and producers as well as a Theatre World Award. The play ran nearly two years, with Ms. Duke in the production (her newly renowned name was swiftly placed above the title on the marquee) for almost that entire time.

Both Ms. Duke’s co-star, Anne Bancroft, and director, Arthur Penn, joined her for the film version of the play, which won the young actress an Oscar as Best Actress in a Supporting Role, as well as a Golden Globe Award. (Her most famous vehicle would stay with her through the years. In 1980, she played Sullivan in a television movie of the play. She won an Emmy Award for her performance.)

Her new fame led to her own series, The Patty Duke Show, created by playwright, screenwriter and producer Sidney Sheldon which ran from 1963 to 1966. At the time, she was the youngest actor to have achieved a self-titled television show. The show was the tonal opposite of The Miracle Worker. In the sitcom, she played the improbable dual role of identical teenage cousins (!), the urbane Cathy Lane and the everyday Patty Lane, who to live together with Patty’s father, a newspaper editor. The nutty plot was aptly conveyed in the catchy theme song, which ran “They’re cousins/Identical cousins all the way/One pair of matching bookends/Different as night and day.”

She also had a recording career at this time, as did many teen stars of her era. Two songs, “Don’t Just Stand There” and “Say Something Funny,” reached the Top 40.

In 1964, she was nominated for an Emmy Award for The Patty Duke Show. She was also nominated for a number of television movies and guest appearances, including A Family Upside Down (1978), Having Babies III (1978), The Girl on the Edge of Town (1981), The Women’s Room (1981), George Washington (1984) and Touched by an Angel (1999). She won Emmys for My Sweet Charlie (1970), as a pregnant teen on the run, and Captains and the Kings (1977). She won a Golden Globe Award for Me, Natalie in 1970.

Her performance as pill-addicted Hollywood star Neely O’Hara in the 1967 camp classic Valley of the Dolls established Duke’s cult status.

Despite her ample success as an actress, Ms. Duke’s life was often turbulent and miserable. The Rosses controlled her income and gave her little personal freedom. She developed addictions to alcohol and prescription pills while still a teenager—again thanks to the Rosses, whom she also later accused of sexual abuse. When she reached adulthood at 18, she discovered the couple had spent much of her fortune.

She also suffered from bipolar disorder, though she would be diagnosed until 1982. She wrote about all this and more in a memoir, Call Me Anna. The book was made into a 1990 television movie, with Ms. Duke playing herself as an adult.

She was married four times: to director Harry Falk (1965-67); Michael Tell (a quickie marriage in 1970 for 13 days at a time when she had learned she was pregnant); actor John Astin (1971-85); and drill sergeant Michael Pierce (1986 to her death). She is survived by Mr. Pierce and their son, Kevin, and two other sons, the actors Sean Astin and Mackenzie Astin. Though given John Astin’s name, biological testing later proved Sean to be the son of Michael Tell.

Duke returned to Broadway late in her career, taking over the role of Aunt Eller in the 2002 revival of Oklahoma!

Here is a video clip of Duke leading the chorus singing “The Farmer and the Cowman” in the 2002 Macy's Thanksgiving Day Parade.