Autopsy report reveals Robin Williams had Lewy body dementia

Actor Robin Williams' coroner's report reveals he suffered from a disease called Lewy body dementia. The autopsy report also shows that there was no alcohol or illegal drugs in his system. Lewy body dementia is a disease few have heard of, but an estimated 1.3 million people suffer from.

CNN's chief medical correspondent Sanjay Gupta breaks down the disease.