Action star Bruce Willis has been diagnosed with untreatable dementia, his family said Thursday, less than a year after he retired from acting because of growing cognitive difficulties.

The 67-year-old US actor known for his role in the Die Hard franchise stepped away from Hollywood in March and has been out of the limelight since then.

"Since we announced Bruce's diagnosis of aphasia in spring 2022, Bruce's condition has progressed and we now have a more specific diagnosis: frontotemporal dementia," a statement said.

Frontotemporal dementia (FTD) is an umbrella term for disorders affecting the areas of the brain that deal with personality, behaviour and language.

"Unfortunately, challenges with communication are just one symptom of the disease Bruce faces," the family statement said. "While this is painful, it is a relief to finally have a clear diagnosis.

"Today there are no treatments for the disease, a reality that we hope can change in the years ahead."

Click 'read more' to see the Willis family statement.