Actor Bruce Willis has frontotemporal dementia, his family announced recently.
In a statement on social media, they said it was a "relief to have a clear diagnosis".
The 67-year-old was diagnosed with aphasia, which causes difficulty speaking, in the spring of last year, but it has progressed and he has been given a more specific diagnosis, the family said.
They expressed their "deepest gratitude for the incredible outpouring of love."
The family went on to say that frontotemporal dementia is the most common form of dementia in people under 60.
"Today there are no treatments for the disease, a reality that we hope can change in the coming years," the statement said.
Willis became a household name in the 1980s and 90s after starring in blockbusters such as Die Hard, The Sixth Sense, Armageddon and Pulp Fiction.
He has also been nominated for five Golden Globes - winning one for Moonlighting - and also three Emmys, winning two.
But his family said last year that Willis would give up acting as his aphasia was affecting his cognitive abilities.
Dementia is not a specific disease, but is actually a group of symptoms that affect intellectual and social skills so severely that they interfere with the person's daily functioning.
