When Dr. Huda Zoghbi thinks back on meeting Henry Engel, son of NBC News chief foreign correspondent Richard Engel, she pictures his face.
"He has this smile that he looks at you — you'll see it in the pictures posted on the web — and naturally, you fall in love with him," she told TODAY. "And you see him — how he's struggling to really do the best he can so he can move, so he can gain some strength to crawl or do something."
"You feel the pain of Rett syndrome, and I felt that pain with so many patients before him," she continued. "You see a child who is helpless and who is sweet, and he’s connecting with you, but he really is suffering from this disease. Your heart goes out, and you want to do everything possible."
Henry Engel died at age 6 earlier this month after being diagnosed with Rett syndrome as an infant.
Rett syndrome is a rare genetic neurological disorder caused when a gene called MECP2, found on the X chromosome, doesn't function properly, in almost all cases due to a mutation on the gene, according to the National Institutes of Health. As a result, the patient will have "severe impairments, affecting nearly every aspect of the child’s life: their ability to speak, walk, eat, and even breathe easily," according to the International Rett Syndrome Foundation.
Because Rett syndrome involves the X chromosome, which females have two of, it's even more rare and more severe in males because they only have one X chromosome, explained Zoghbi, director of the Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital. Males are more likely to die from the illness.
She recalled that she met Henry within his first year of life after Richard Engel and his wife, Mary, noticed their son wasn't reaching usual motor milestones — the first sign of Rett syndrome for many children, according to the foundation. After sequencing was performed on Henry, it was discovered that he had a mutation to the gene involved in Rett syndrome. The Engels got in touch with Zoghbi, who's been researching the disease for many years.
Zoghbi then uncovered that Henry was the first person observed to have his particular mutation to the MECP2 gene. Naturally, she needed to do more research, so she recommended Henry be seen at Texas Children's Hospital, where doctors could treat and track his symptoms to see if they followed the usual path for Rett syndrome.
"When we first met Henry ... he couldn't stand steady. He had a tremor. He would shake a little bit," she recalled. "He couldn't speak, but he was young. He had a lot of different weaknesses in his motor system."
She added that Henry’s parents “worked so hard” to help him, doing physical and occupational therapy with him every day and advocating for research in hope that it could save their son and thousands of others.
"It was really amazing watching them work as a team," Zoghbi said. "One of the visits, I was so excited because he did say, 'Dada.' That was a word we heard from him."
Due to the pandemic and the Engels being based in the U.K., she didn't see Henry for two years prior to his death. But she was aware that his condition started to worsen a few months ago "in spite of the heroic effort his parents were doing with him," she said. "That's the nature of this disease."
Zoghbi attributes the fact that Henry lived longer than most boys with the disease to his parents, in part. "(They) really worked very hard to protect him and give him physical therapy so that he could be as functional as possible," she said, adding that many boys with Rett syndrome die by age 2.
Another standout moment from her time with Henry was one of his birthdays.
"I got some books, and the smiles I got from him — he was happy," she said. "He must have recognized everybody was celebrating him and everybody's excited about it. He was so happy and active. That's really my last memory during his last visit."
"This is the memory I'll always hold dear because he reacted to the books we gave him and the toys. It was fun. ... It was a special time."
As a geneticist and researcher, Zoghbi also values the moment that Henry met her team of students and scientists researching a cure for Rett syndrome. Currently, there isn't one, and treatment addresses symptoms, not the cause of them, according to NIH.
"When they’re working in the lab, they’re always thinking about him,” she said.
In fact, because of Henry's unique mutation, Zoghbi's team is using Henry's cells in ongoing research. By studying Henry's cells several years ago, she learned that Henry's mutation affected the function of the MECP2 gene in such a way that it caused an important protein for brain development to be produced at lower levels.
"That inspired us to start thinking of different ways where we can increase the protein that's made by this gene," Zoghbi explained. "So if it's not functioning at 100% capacity — maybe it's functioning at 40% capacity — maybe if we can increase the amount of the protein, maybe that will get us to help some of the symptoms."
"(Henry) became a driving force in the lab because the lab members met him and knew him and played with him," she added. "This kind of relationship is very important because it reminds everybody in the lab that there are human beings at the end of the road who are waiting and may one day benefit from this work."
"Henry helped us make a very strong connection," she continued. "You just can’t help it. His sweet smile, he’s so good. He just will smile and light up your day."
But research takes time, and Zoghbi said she's "heartbroken" that she and her team weren't able to bring to the table something that could help Henry directly. Many of the people who work in the lab were also devastated by Henry's passing, but they were quick to tell Zoghbi, "We're going to continue to work. We're so close. That's what we have to do," she recalled.
While Henry's cells are still being used in her research, Zoghbi stressed that she's learned so much from so many Rett syndrome patients on her path to find a cure.
"I love all of them," she said. "I worked 16 years to find the (MECP2) gene. I care about all of them."
And Henry could still help Zoghbi give these patients and their families what they've been waiting for.
"Studying (Henry's) cells helped us to think a little differently, to find yet one more approach for developing therapies for Rett," she said. "If we're successful, that can help so many patients. That would be a dream. That would be (Henry's) legacy."