Actor Bruce Willis, 67, has been diagnosed with dementia, his family revealed on Thursday in a statement.

Willis retired from acting last year after he was first diagnosed with aphasia.

What do we know about the diagnosis?

His family announced the development, saying that his condition has progressed and he has now been diagnosed with frontotemporal dementia (FTD).

"Bruce always believed in using his voice in the world to help others, and to raise awareness about important issues both publicly and privately," his family said in a statement.

"We know in our hearts that — if he could today — he would want to respond by bringing global attention and a connectedness with those who are also dealing with this debilitating disease and how it impacts so many individuals and their families," the statement added.

His family said that Willis faces "challenges with communication," among other symptoms.

A version of the statement was also published on the The Association for Frontotemporal Degeneration website. It was signed by Willis' current spouse Emma Hemming Willis, his ex-wife Demi Moore, and his five children: Rumer, Scout, Tallulah, Mabel and Evelyn.

Beloved Hollywood star

Willis is best known for his roles in action films such as 1988's "Die Hard" and Quentin Tarantino-directed "Pulp Fiction" in 1994.

He first rose to prominence in the 1980s as detective David Addison Jr. in comedy-drama TV series "Moonlighting."

Willis was born in 1955 in Germany to an American father and a German mother. He battled stuttering as a child.