Ronald Reagan’s daughter, actress Patti Davis, is sharing her sympathy and advice to Bruce Willis and his family after the recent announcement of the actor's frontotemporal dementia diagnosis.

In an opinion piece written for the New York Times, Davis, 70, reflected on her father’s decision to go public with his diagnosis of Alzheimer’s disease in 1994.

The former president had been out of office for five years when he wrote a letter to the country that detailed his condition. 

Davis shared her memory of her mother, Nancy Reagan, calling her to tell her they were releasing the letter. "She said it was his idea, and she was so proud of his decision," Davis wrote.

Patti Davis, Paul Grilley, First Lady Nancy Reagan, President Ronald Reagan, daughter-in-law Doria, and son Ron.

Patti Davis, left, was Ronald and Nancy Reagan's only daughter. (Bettmann / File)

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She continued, "I wasn’t surprised – of course he would want the country to know. His love and loyalty to America ran deep. And I shared my mother’s pride in him for being so honest. She said he had just sat down, taken pen and paper and begun writing."

The former first daughter went on to share her concerns for the "Pulp Fiction" star and his family, noting the differences in the diseases.

"Bruce Willis and his family may have a harder road to travel than my family did," she wrote. "Frontotemporal dementia is radically different from Alzheimer’s. People with the condition can become unrecognizable in their outbursts, their aggressive and voracious behavior."

She further explained the "two main variants" of the diagnosis: one having to do with behavior and the other with language, or aphasia, with which Willis had previously been diagnosed. Aphasia is the loss of language comprehension, which Davis said can be "traumatic."

"That’s the other curse of frontotemporal dementia," she added. "It usually strikes people when they are younger, often in their 40s or 50s." Willis is 67 years old and was first diagnosed with aphasia last year.

Last week, the "Die Hard" star’s family shared a statement that announced his diagnosis of frontotemporal dementia (FTD).

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It read, "Our family wanted to start by expressing our deepest gratitude for the incredible outpouring of love, support and wonderful stories we have all received since sharing Bruce’s original diagnosis. In the spirit of that, we wanted to give you an update about our beloved husband, father and friend since we now have a deeper understanding of what he is experiencing." 

The actor’s daughter, Scout Willis, shared her thoughts on her father's "cruel" diagnosis on her Instagram stories not long after the announcement.

"Feeling emotionally tired and a bit overwhelmed, yet also very in awe of the love so many people have for my papa," she wrote alongside a photo of herself. Her sisters, Rumer and Tallulah, both of whom are also from Willis' marriage to actress Demi Moore, echoed similar sentiments in the comments of her post.

Demi Moore Scout Willis Bruce Willis

Demi Moore, Scout Willis and Bruce Willis (Instagram: Scout Willis)

"Second this Scouter," Tallulah wrote. "Feeling the abundant love for our guy and our family."

Rumer added, "I third this Scouter and [Tallulah] feeling so deeply grateful and in awe of the love for us and our sweet Daddio."

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Davis, who started the support group Beyond Alzheimer’s for caregivers and families, offered advice not only for the Willis family but those around them.

"My hope for Bruce Willis’s family, as they go down this unpredictable and heartbreaking road, is for those around them to know that simply being there is often all you can do," she wrote. "There is no sidestepping the grief, the pain, the helplessness. There is just, maybe, a human wall of comfort to lean on."

Bruce Willis attends event

Bruce Willis is battling dementia after his aphasia diagnosis progressed. (VCG)

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She concluded by thanking the Willis family for their willingness to be open about the diagnosis, saying that "there are others whom the Willis family will never meet, other families who have been invaded by this cruel disease, who today feel a little less lonely because of the decision to announce a diagnosis that rips your soul apart."