Michael J. Fox 'Stunned' By Robin Williams' Parkinson's Diagnosis

On Friday, Robin Williams' wife, Susan Schneider, revealed the late actor had been suffering from the early stages of Parkinson's disease - a chronic and progressive movement disorder with symptoms that worsen over time.

While Schneider said "he was not yet ready to share publicly" the news of his disease, actor Michael J. Fox has been very public with his Parkinson's since being diagnosed in 1992.

Following Thursday's revelation about Williams' health, Fox tweeted to his nearly 1.2 million followers:

Stunned to learn Robin had PD. Pretty sure his support for our Fdn predated his diagnosis. A true friend; I wish him peace.

- Michael J. Fox (@realmikefox) August 14, 2014

Longtime pals, Fox also tweeted after news of Williams' death on Monday:

Famously kind, ferociously funny, a genius and a gentle soul. What a loss. #RobinWilliams

- Michael J. Fox (@realmikefox) August 12, 2014

Last year, Fox - who has become the de facto face of Parkinson's - even played a character who suffered from the disease on the short-lived NBC sitcom, "The Michael J. Fox Show."

Parkinson's Disease affects nearly one million people in the U.S.

The Parkinson's Disease Foundation notes that the cause of the disease "is unknown, and although there is presently no cure, there are treatment options such as medication and surgery to manage its symptoms."

In Williams' wife's statement on Thursday, she expressed: "It is our hope in the wake of Robin's tragic passing, that others will find the strength to seek the care and support they need to treat whatever battles they are facing so they may feel less afraid."