Former child actress Patty Duke, who was one of the youngest Oscar winners for her role as Helen Keller in The Miracle Worker, died Tuesday of sepsis from a ruptured intestine at the age of 69.

She's probably best known for starring in the 1960's sitcom The Patty Duke Show, where she played identical cousins Patty and Cathy Lane.

She went on to star as the alcoholic, drug abusing singer Neely O'Hara in the film Valley of the Dolls, and won an Emmy in 1970 for her role as a pregnant runaway teenager in the TV-movie My Sweet Charlie.

Duke revealed in her autobiography, Call Me Anna, that she had been diagnosed with bipolar disorder, which prompted her to become an advocate for mental health, working with the National Institute of Mental Health and the National Alliance on Mental Illness.

She leaves three children, actors Sean and Mackenzie Astin, and Kevin Pearce.