Platt, who was formerly married to film director Peter Bogdanovich, produced a string of successful movies including Broadcast News and War of the Roses.
Her daughter, Sashy Bogdanovich, said Platt died on Wednesday of a form of motor neurone disease.
Platt leaves two daughters and three grandsons.
Born in Illinois, she studied art at the Carnegie Institute of Technology in Pittsburgh, before she began her career as a costume designer for the stage.
She worked with husband Bogdanovich, as a set designer, on films including The Last Picture Show, but they separated following his affair with the film’s star Cybill Shepherd.
After the divorced in 1971, however, they maintained a working relationship on hit films such as What’s Up Doc?, starring Barbra Streisand, and Paper Moon.
Platt was also known for her long professional association with Terms of Endearment director James L Brooks, and was executive vice-president of his production company, Gracie Films.
In the early 1980s she presented Brooks with a cartoon strip written by the then-unknown Matt Groening – who would later go on to create The Simpsons. Brooks went on to become a long-standing writer and developer on The Simpsons series.
Source : BBC