Michael J. Fox's reaction to hearing Robin Williams had Parkinson's disease

Michael J. Fox has been the most recognizable face of Parkinson's disease for decades now. The "Back to the Future" and "Family Ties" actor was diagnosed with the disease in 1991 and disclosed his condition to the public in 1998. Since that time has been at the forefront of many philanthropic endeavors to battle Parkinson's, including starting the prominent Michael J. Fox Foundation for Parkinson's Research. Still, Fox had no idea that the recently deceased Robin Williams was suffering from Parkinson's.

Below a tweet from Michael J. Fox's account on August 14 after it was revealed by Williams' wife that her husband had Parkinson's.

Previously Fox had tweeted "Famously kind, ferociously funny, a genius and a gentle soul. What a loss. #RobinWilliams" after first hearing the news that Robin Williams had died. But with this new addition in his tragic death, Williams has become another face of those who are battling or have battled Parkinson's disease in their lifetime.