Robin Williams’s death left three kids, a wife, friends, and millions of fans in the wake of his death wondering why such a brilliant comedian would take his own life. At first, reports said his depression mixed with Parkinson’s disease diagnosis was the root of his suicide. They were wrong — Williams did not have Parkinson’s disease, but instead a much more complicated and unheard of condition that left him battling with hallucinations in the days leading up to his death. It was announced on Tuesday he had Lewy body dementia (LBD), a type of dementia and Parkinson’s disease hybrid.

"In the news you are more likely to hear about Alzheimer's and Parkinson's disease," Dr. Zianka Fallil, a neurologist at North Shore-LIJ's Cushing Neuroscience Institute, told the NY Daily News. "The general population is not aware of the subtype of Lewy body dementia as they probably should be, and it's mostly because a lot of times when families bring patients to clinics they may not speak of other issues going on — paranoia, hallucinations, delusions — unless elicited specifically. If you look at the complete clinical picture, it might be Lewy body dementia."

Although it’s not as commonly heard of as Parkinson’s or Alzeihmer’s disease, it still affects 1.3 million Americans. Dr. Frederick H. Lewy discovered Lewy bodies, abnormal deposits in the brain, while he was working in Dr. Alois Alzheimer’s laboratory in the early 1900s. Despite being the third most common cause of dementia after Alzheimer’s and vascular dementia, researchers still aren’t sure how it functions in the brain, according to the Alzheimer’s Association. When Williams’s condition was revealed and confirmed by TMZ, which had sources connected to the comedian’s family, it came as a shock. LBD can cause a “progressive decline in mental abilities as well as visual hallucinations, which generally take the form of objects, people, or animals that aren’t there,” according to Mayo Clinic.

After Williams’s body was discovered in his California home Aug. 11, his wife Susan Schneider confirmed he was in the early stages of Parkinson’s disease and also suffered from anxiety and depression. LBD’s disease progression has a very similar sequence and symptomatic process as Parkinson’s disease. Both diseases are caused by a small misfolded protein in the brain called the alpha-synuclein and causes problems with thinking and reasoning. Lewy bodies affect six different areas of the brain, including the limbic cortex, which plays a major role in emotions and behavior, as well as the cerebral cortex, which controls information processing and perception, according to the National Institute on Aging.

There are two different types of LBD. Dementia with Lewy bodies has cognitive symptoms that appear within a year of movement problems, and then there’s Parkinson’s disease dementia. Not only is Parkinson’s disease a devastating disorder that affects the nervous system and gradually worsens movement, speech, and causes tremors, but it also causes cognitive issues in LBD cases.

Lewy body dementia is "very complex, and it requires treating a much broader range of symptoms to maximize quality of life," Angela Taylor, director of programs at the Lewy Body Dementia Association, told CBS News. "The report indicates that [Williams] was being treated for Parkinson's and that is one of the features of dementia with Lewy bodies. Hallucinations are a core feature of Lewy body dementia."

As his loved ones and fans struggle to rationalize how one of the greats took his own life, they may find solace in understanding his disease better. Shining a spotlight on LBD may be the only way to help prevent those struggling with the same fate before it’s too late.