Bruce Willis has frontotemporal dementia. So did my dad.

Like the rest of the world, I learned Thursday that Bruce Willis — the man we all know from Die Hard and Moonlighting — has frontotemporal dementia. I caught my breath at the headline but didn’t process the news until the quiet of night, as I was trying to fall asleep.

Willis has frontotemporal dementia. Just like my dad.

It is a big deal to me because people don’t mention frontotemporal dementia very much. Only a small handful of people with dementia — just 2%, according to one estimate — have the frontotemporal kind, so at my monthly support group for caregivers of people with dementia, all the talk was Alzheimer’s, which makes up the vast majority of cases. The support group was helpful, but I still often felt alone.

When you say the word dementia, most think of a person with Alzheimer’s, who can walk and talk and maybe even dress themselves, but doesn’t remember key facts about their life, such as where they live or who their children are.

I have a dear family friend with Alzheimer’s. The last time I saw him, we had a lovely chat, talking about his favorite dogs he’s owned over the years. He looked and acted just like he always had, so for brief moments, I could pretend that he wasn’t sick. Then, at one point, he turned to me and asked: “Do you know Alison McCook?”

I couldn’t help but take advantage. “Oh yeah, she’s great.” I smiled, and he smiled back, with a look of pride in his eyes. In that moment, I got to see what he thought of me when I wasn’t there, how much he loved me. I hope I never forget it.

But let’s be clear: Alzheimer’s is not full of heartwarming moments. It is cruel, grueling, and often unbearable — both for the person and the people who love them.

Frontotemporal dementia is also cruel, grueling, and often unbearable. But in a very different way.

My father’s first symptom was aphasia — the loss of words, beyond a “whatchamacallit” moment. Here, too, dad was the odd man out, as most people — like Sen. John Fetterman — develop problems with language after a stroke. So at the aphasia support groups my dad attended at Moss Rehab, there was the prospect, for some patients, of improvement. With therapy, hard work, and time to heal, they might regain some of what they lost.

That’s not what happens with frontotemporal dementia.

Instead, over the course of 10 years, my dad went from losing a few words here and there to losing entire sentences. Often I could figure out what he was trying to say, but that got harder, as frontotemporal dementia can change your personality (another way it is often different from Alzheimer’s). He went from someone who always had a good mood and a funny story to little more than a primal ball of want.

He wanted to sit in his recliner all day, eat sweets, and watch TV. And whenever something interrupted that — a doctor’s appointment, for instance — he became enraged. So much of my life was spent trying to placate him, to visit as much as I could to put on his favorite movie (inexplicably, a 1990 Western starring Tom Selleck as a cowboy in Australia, Quigley Down Under), feed him ice cream and Diet Coke, and find caregivers to watch him when I wasn’t there. For more than a decade, I didn’t work full time so that I could attend to his needs, take him to the doctor, and pay his bills.

Unlike Alzheimer’s, which happens more often in older people, frontotemporal dementia typically strikes at a much younger age; I suspect it started long before my dad was diagnosed in his early 60s. It was a lonely time, when many of my friends — whose parents were still healthy — couldn’t relate.

After he lost his language, he began to lose his body. He needed help walking, dressing, and going to the bathroom. But even when he was in a wheelchair, and the only word he said he screamed — “NO!” — he always knew who I was, and seemed happy to see me. I’ll never stop being grateful for that.

That is a key difference between frontotemporal dementia and Alzheimer’s: Frontotemporal dementia took my dad’s exterior life — his voice, his body, his personality — but his interior life, his memories, who he was and who he loved, were often still there. My family friend, on the other hand, can still walk and talk and seem like himself sometimes; he just may not know who you are.

Eventually, my dad’s exterior life — his body — wore down, and he died in September 2020.

I don’t know why Bruce Willis got frontotemporal dementia, and I don’t know why my dad did, either. Up to 15% of cases are inherited. (But I don’t like to think about that.) A frontotemporal dementia expert at Einstein Medical Center told us it might stem from my dad’s years of heavy drinking, or a series of head injuries he experienced as a boy. Don’t let your daughter play high-contact sports, he urged me, with the implication clear: This could happen to you, or her. (But I don’t like to think about that.)

I don’t hear about many other people with frontotemporal dementia. So the news about Willis is hitting me hard. To his family, I say: It’s cruel, grueling, and often unbearable. But you’re not alone.