A family’s medical ordeal after losing one of their own to a rare illness has inspired them to get out the word and help others.

Kaelyn Kastle, a singer with a large social-media following, said she had been able to help a woman in the United States struggling to find out what was happening to her young son — who turned out to be battling against the same autoimmune disease that claimed the life of her mother, Donna.

“I just wanted to tell her story — you just never know who it could save,” she told The Royal Gazette.

Mrs Castle died from an obscure disease, sarcoidosis, which cut short her athletic career in her youth.

Decades later, the chronic illness returned as renal pulmonary vasculitis, which baffled physicians in Bermuda.

Doctors initially mistook her constant dry cough for one of the telltale symptoms of Covid-19.

Kaelyn said doctors “could not figure out what it was and tested for everything, including pneumonia” in 2022.

The dry cough built into cold symptoms and then turned aggressive.

“She couldn’t breathe,” Kaelyn said. “Her whole airway was closing up.”

Sarcoidosis causes the immune system to attack the body in a variety of ways. It frequently affects the lungs, causing shortness of breath — known as pulmonary sarcoidosis.

The disease’s assault on Mrs Castle’s kidneys marked the renal component of the illness, while vasculitis was the immune system’s devastating attack on otherwise healthy blood vessels, causing chronic inflammation.

Her husband, Kenneth “Jack” Castle, said: “What we would like to do is explain to the public my wife’s condition.

“What has happened since her passing is people have been asking us about it, saying they didn’t know that she had ‘cancer’ — people are asking a whole lot of questions that show they just are not aware of what she had.”

Kaelyn, who credited her mother with nurturing her talent as a performer, said the illness was “so rare that only about one in 100,000 people get the disease”.

“Just a random person from Bermuda had it. But my big thing is I wanted to educate the public. I’m a social-media girl. One story can change someone’s life.”

Mr Castle said: “My wife and I have been together since she was 17. Donna wanted to run for Bermuda in Jamaica.

“Once she came back, she had breathing issues, and she was sent to Johns Hopkins. She was over there for months. They treated her with steroids.”

Mrs Castle appeared to improve. Her family said she was notable for spending most of the rest of her life never appearing to get sick.

Her daughter explained: “It’s known to come on at a young age, before you are 25. It also comes back after the age of 45.

“In my mom’s case, it lay dormant in her body for 43 years.”

Mrs Castle abruptly fell ill in 2022 with something that started as an apparent cold, with a dry cough caused by inflammation as her own cells attacked her lungs.

Her family said they have been left with a host of unanswered questions.

However, they speculated that Mrs Castle’s use of turmeric, a spice believed to have anti-inflammatory properties, might have helped to keep her symptoms at bay.

They said physicians at the hospital in Bermuda treated what they took to be an infection, using antibiotics.

Eventually, Mrs Castle was put on a ventilator, but the disease then moved to her kidneys, resulting in her having to be on constant dialysis.

The family flew her to Brigham and Women’s Hospital in Boston, where doctors struggled for ten days to diagnose her condition before identifying sarcoidosis as the culprit.

Mr Castle said: “They told me there were just 60,000 people within the US who had it. It was really rare.”

Mrs Castle’s condition had no cure, but she joined a medical trial of people being treated with a combination of steroids and the drug Rituxin, under the brand name Rituximab.

Even so, she had to be revived twice from cardiac arrests while in Boston.

Her family brought her home in May 2023, but her illness eventually returned in a new form of vasculitis, which caused a host of infections, followed by vertigo and weight loss, and then a seizure.

Her husband and daughter said doctors in Bermuda again struggled to treat her, until a physician got in touch with Brigham and Women’s, where she returned in April this year for another round of treatment.

Twenty days later, on May 17, she died there with her husband at her side.

Kaelyn said: “The reason why this story is so important to spread is because of social media and TikTok.

“I use TikTok like a search engine. It’s practically as good as Google, which is why I’ve been part of the fight to keep TikTok.”

The wildly successful app faces being banned in the US over data-privacy concerns.

Kaelyn said she had shared her research through TikTok and searched for others enmeshed in the medical battle over sarcoidosis, so that the family can use their experience to help others to find treatment and feel less alone.

Several months ago, she left a comment among “thousands” on the page of a Connecticut woman desperately trying to figure out what was making her young son so ill.

“Now she is on the same journey with Rituximab,” Kaelyn said. “She said that’s what saved her son.”

She added: “I feel like I’ve been able to do my part on social media.”

Donna Castle sent her daughter to her first singing lessons, and bought her a guitar as a surprise gift, which Kaelyn still owns.

She said her mother’s “intelligence, creativity and work ethic have been instrumental in making me who I am”.

In her funeral tribute to her mother, she said: “She has done her work.

“As much as I know, there’s so many more things my mother wanted to do with us before she left, so many plans she had, she’ll be for ever with my brother [Casey], father and me.”