What is aphasia? Many people want to know more about the disorder after it was announced that Bruce Willis had been diagnosed and would be stepping away from his acting career.

Rumer Willis, Bruce’s daughter, posted the news to Instagram on Wednesday, “To Bruce’s amazing supporters, as a family, we wanted to share that our beloved Bruce has been experiencing some health issues and has recently been diagnosed with aphasia, which is impacting his cognitive abilities.”

Aphasia is more of a symptom than a true diagnosis. Someone with aphasia has issues with language and communication. It’s often caused by an underlying problem in the brain, most commonly on the left side of the brain.

“It’s really quite something that aphasia affects over 2 million people in the United States. And it’s actually more common than Parkinson’s disease, cerebral palsy, and muscular dystrophy combined and yet hardly anyone knows what it is,” Dr. Carol Persad, Director of the University of Michigan’s Aphasia Program, said.

Read the full article at WDIV-TV.