It was with the pomp and intrigue of a Dan Brown novel that earlier this month Pope Francis made his way into the Aula Paolo VI audience hall, a room the size of an aeroplane hangar in Vatican City. Flanked by the flamboyant Swiss Guard and dark-suited men muttering into earpieces, he headed for an oversized chair on a stage in front of nearly 2,000 people. Many applauded, most gawped in disbelief.

The pope was there to do something no other world leader has done before. He was meeting people with Huntington’s disease, a rare and incurable neurological disorder that has long been shrouded in shame and discrimination. It’s a genetic disease that runs in families. It causes involuntary jerky movements and can make people depressed or aggressive, symptoms that can leave them socially isolated, thanks in part to a historic misunderstanding.

The Vatican has access to very relevant people – whoever the pope puts in charge can use that influence to really help Claudia Perandones, neurologist

“In centuries gone by, people thought it must be some sort of curse, or witchcraft, or that someone had offended the gods,” says Charles Sabine, a journalist who co-organised the event – and is a gene carrier for the condition. “In the early 20th century the eugenics movement in America suggested sterilising people with the disease. The Nazis took it a step further and put them in gas chambers. The culmination of all this, not surprisingly, especially in more remote parts of the world, is a massive stigma attached to the disease that means many people who are affected by it do not admit it.”

The event was part of a campaign called HDdennomore, pronounced “Hidden no more” (HD is an acronym for the disease), which aims to relieve families of this stigma, particularly those in poor communities in South America where the condition is most common. The Observer was invited along after we published a feature highlighting the plight of people with Huntington’s living in Colombia and Venezuela. No Pope, says Sabine, had so much as uttered the words Huntington’s disease before. Addressing the crowd on 18 May, Pope Francis spoke warmly, telling people that they are all precious in the eyes of the church. He then spent nearly an hour with about 150 patients, their families and their carers, greeting and hugging them one by one.

Facebook Twitter Pinterest Photograph: Pier Paolo Lisarelli

“It was spectacular,” says Nancy Wexler, a US scientist who co-discovered the gene that causes the disease. “It meant so much to hear him say the words ‘Huntington’s disease’, to say that he understood the problems, that it was a genetic disease and that it is nobody’s fault.”

Many families hide the disease because they fear their employers, insurance companies or prospective mortgage lenders will find out. “Huntington’s disease is the vanguard of much broader questions about healthcare that will affect us all,” says Sabine. “Questions about health and genetic data privacy from companies, big moral questions about whether it’s right to use Crispr gene-editing.” Crispr is a nascent but potentially wide-reaching technology that might one day be used to excise the disease-causing gene from embryos.

The event’s other co-organisers were two Huntington’s scientists: Elena Cattaneo from the University of Milan, who is also an Italian state senator, and Ignacio Munoz-Sanjuan from the CHDI Foundation, who runs Factor-H, a humanitarian project to help poor families with the disease in South America.

In spending their careers looking for a treatment, both have been gripped by the need to care for people who live, and die, with little if any social or medical care. “I am a scientist and I want to contribute,” Cattaneo said before the event. “[Finding a treatment] should be manageable because we know the cause of the disease, but right now these people are left alone.” Her first letter to the pope asked him to meet only one patient from Venezuela. The event ballooned after Pope Francis asked to learn more and said he wanted to help.

Ultimately the event was attended by families from 23 countries. With help from donors, HDdennomore brought families from Venezuela, Colombia and Argentina. Among them were two children with early-onset symptoms that have caused both to be cast out by their schools and playmates.

Facebook Twitter Pinterest Anyervi, 13, and Brenda, 15, who both have early-onset Huntington’s. Photograph: Pier Paolo Lisarelli

Before the pope arrived, Sabine surprised both children with gifts on stage. To Anyervi, a 13-year-old boy from Venezuela, he presented a football that was used in a Champions League game, a Barcelona shirt signed by his favourite player – Brazilian star forward Neymar – and a personal message from the man himself, played on a jumbo screen. “I bet the other kids will let you play with them now,” Sabine said, as Anyervi returned to his seat, smitten with his haul.

Next up was Brenda, a 15-year-old girl from Buenos Aires, accompanied by her neurologist, Claudia Perandones. Brenda’s father died from the disease on her last birthday. Her mother abandoned her when she started showing symptoms. Coaxed by Sabine, she gushed about her favourite singer, the Latin superstar Axel, as unseen by her he was tip-toeing up behind her holding his guitar. As he began to sing, she was struck by such cartoonish awe you could see the back of her mouth and whites of her eyes from a mile away. It would have brought a tear to the eye of even the most hardened science correspondent.

Scientists and doctors working in Huntington’s disease will be making wishes too. “We face a lot of problems,” Perandones said before the event. “In South America, we have to fight for most simple things for patients like food, water, clothes, the possibility of going to school. Many times I’ve asked authorities for help and it’s been a nightmare.” The pope’s endorsement might make future bargaining easier. “We are sure this is not just a hello, I bless you, good bye. We know that the Vatican has access to the relevant people, and whoever the pope puts in charge of this can call and use that influence to really help these people in the way they need it.” Those calls could be to presidents, health ministers, or even CEOs of drug companies.

In his address, Pope Francis commended scientists for their work, but drew a line in the sand when it came to the use of human embryos in research. It seemed unnecessary, given the nature of the event.

“That wasn’t helpful,” says Anne Rosser, a Huntington’s scientists from Cardiff University who was not there. “Like many scientists, I’d politely but very firmly disagree. Stem cells, including embryonic stem cells [undifferentiated cells from embryos only 16, 32, or 64 cells large], have been and will go on being important in actually finding a treatment for this disease.”

These cells, she says, help scientists learn more about the disease and might one day be used in regenerative treatments to replace brain cells lost to the condition.

Women living with this hereditary disease need autonomy over how, when, and if they start a family. That includes personal decisions about contraception and embryo selection with IVF. These are old and entrenched battle lines between public health and religion – progress will be made very gradually – but this papal audience represented a big first step.

“I’ve got the utmost admiration for the scientists there,” says Rosser. “Those working on stem cells put themselves in an uncomfortable position for the good of the Huntington’s community and raising awareness.”

It was a job well done. As the families with Huntington’s disease left the Aula Paolo VI and dispersed into the throngs of tourists milling around the Vatican, they did so with their heads held that little bit higher.