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, AFP reported. "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.