Everything Richard Engel Said About 'Beloved' Son's Journey with Rett Syndrome Before His Death

Richard Engel has long been outspoken about his son's difficult experience with Rett Syndrome, a rare genetic neurological disorder, in the years before his death.

The NBC News chief foreign correspondent, 48, announced on Twitter Thursday that his 6-year-old son had died after a years-long battle with the disorder. Henry, whom Richard shares with his wife Mary, died on Aug. 9, according to a memorial page on the Texas Children's Hospital website.

"Our beloved son Henry passed away. He had the softest blue eyes, an easy smile and a contagious giggle. We always surrounded him with love and he returned it, and so much more," Engel wrote.

"Researchers are making amazing progress using Henry's cells to help cure RETT Syndrome so others don't have to endure this terrible disease," he added in a follow-up tweet.

Henry was first diagnosed with Rett Syndrome, a rare genetic neurological disorder that leads to severe physical and cognitive impairments and has no cure, as of yet, in 2017.

Engel first spoke to PEOPLE in January 2018 about his son's diagnosis, noting at the time that his son was "probably not going to walk, probably not going to speak, probably not going to have any mental capacity beyond the level of a 2-year-old."

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RELATED: Richard Engel Announces Death of 'Beloved' 6-Year-Old Son Henry

Months later, in October 2018, the journalist opened up in a candid essay for Today about his family's harrowing journey and his son's condition.

At the time, Engel said it was getting "increasingly difficult" to help Henry keep active "because of basic physics," as the parents had to move their son constantly to help keep him engaged in his surroundings — something that has led Engel's wife Mary to start "working out like mad" to keep up with the physical demands of parenting.

"But Henry is making amazing progress," Engel added in his essay. "He's getting stronger. He's sitting up straighter. He can focus for longer. He doesn't talk, but he verbalizes more. In addition to regular physical-therapy sessions, we put Henry for an hour every day in a 'standing frame,' a device that holds him upright."

"We're not giving up by a long shot," he wrote. "We're determined he will walk one day. But working out the complexities of Henry's mind is an even greater challenge than training his body."

"People often ask me — and I appreciate it — how Henry is doing. I don't have a quick answer, but there is hope in this story," Engel continued. "There is even a chance Henry's story could have a fairy-tale, after-school-special ending. Henry's disability is profound, but is also profoundly unique, and anything that rare is valuable. Doctors think Henry's exact genetic mutation is one of a kind. They think — and I'm still blown away by this — that he could hold the secret to finding a cure not only for himself, but for many other children with special needs."

From left: Richard, Henry and Mary Engel

A year later, Engel and his wife welcomed another little boy, son Theodore, into their family and spoke with PEOPLE about the adjustment at home.

Engel said that it would be "difficult" to watch baby Theo pass their son Henry, 3 at the time, with certain developmental milestones.

"We know why there is this differential. And it's going to be hard to watch Theo pass his older brother in terms of capabilities," he said. "That's going to be very difficult for us to see. To see a 1-month-old very soon overcoming his almost-4-year-old brother … that's going to be tough."

Engel also spoke about some of the "setbacks" Henry was going through at the time, including seizures and a "compulsive repetitive motion that [was] becoming more pronounced."

The NBC correspondent revealed that Henry had "hip problems," sharing that there was a possibility their son would need "major surgery" in the future. He also explained that Henry was "lacking a conductor gene" and that a medical team at Texas Children's Hospital was "trying to build a treatment that could help immensely."

When the coronavirus pandemic rolled around in 2020, Engel said Henry's experience became a "nightmare."

"Henry has severe special needs, and COVID has been an absolute nightmare for him and millions of other children like him. I'd add more colorful adjectives, but you get the point," wrote Engel in an essay for Today. "Henry, who turns 5 in September, doesn't walk or talk. He can't feed himself efficiently. He doesn't sit up straight. Now that he's getting bigger, he can barely move independently."

Courtesy Richard Engel Richard Engel's wife Mary and son Henry

He admitted he and his wife Mary "were coping better before COVID," revealing that "school was the only place where [Henry] could interact with other children," which was a huge asset for him.

"We burn scented candles. I do spa baths, combing his wet hair and giving him a head massage with conditioner," he said of their activities at home amid the pandemic. "Mary sings to him, sometimes a song she made up about Coco, and works with flash cards to teach him letters, numbers and colors all day long."

And while "it all helps," Engel said Henry was "still bored, and his condition seems to be getting worse" — but luckily, the family was able to continue the little boy's therapies at home, with a $100-an-hour private therapist.

Engel shared another update on Henry's health this past May, noting that his condition had "progressed" and he had "taken a turn for the worse."

"For everyone following Henry's story, unfortunately, he's taken a turn for the worse," the foreign correspondent captioned a touching clip of Henry with his brother Theo. "His condition progressed and he's developed dystonia: uncontrolled shaking/ stiffness."

He added that Henry was "now home and getting love from brother Theo" after being hospitalized for six weeks.

Later sharing a photo of Henry flashing a grin, Richard wrote, "Thank you everyone for all the kind messages, from Henry, our Mr. Handsome."

Click here to contribute to the continued research efforts at Texas Children's Hospital's Duncan Neurological Research Institute (Duncan NRI).