LOS ANGELES — 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, behavior 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.”

Doctors say the frontal and temporal lobes of the brain shrink in a patient with FTD.

What causes this to happen is not known, but it can result in personality changes, or modifications in behavior that might make someone socially inappropriate, impulsive or apparently uncaring towards those around them.

Other sufferers lose their ability to use language.

The Mayo Clinic says FTD can begin between the ages of 40 and 65, and is the cause of up to a fifth of all dementia cases.

The family statement, signed by Willis’ current wife, Emma Heming Willis, as well as former wife, actress Demi Moore, and his children Rumer, Scout, Tallulah, Mabel and Evelyn, said the actor had always worked to raise awareness about important issues.

“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,” it said.

Willis has been a fixture on the small and large screen since the 1980s, coming to public prominence in the TV series “Moonlighting.”

But it was as hard-bitten hero John McClane in “Die Hard” that he became a bankable major star of the cinema, sparking a career that has generated billions of dollars of box office revenue.

Despite the tough-guy image, he has also had much success with more family-friendly fare, and provided the voice for the baby in the popular “Look Who’s Talking.”

Another of his best-known roles was as the dead person that child actor Haley Joel Osment could see in “The Sixth Sense.”

Reaction from the entertainment industry was swift.

“Love you so much my friend,” wrote “Breaking Bad” star Aaron Paul on Rumer Willis’ Instagram. “Sending hugs to you and that beautiful family of yours. Your pops is such a damn legend.”

“Jumanji” and “Cars” star Bonnie Hunt wrote on Demi Moore’s Instagram page: “An abundance of love for you dear Demi, for Bruce, for all of you.”

Willis won a Golden Globe and two Emmys during his career.