On Thursday, NBC News chief foreign correspondent Richard Engel announced the death of his 6-year-old son Henry.

“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. Mary and Richard,” Engel said on Twitter.

The TODAY regular shared a link to the Texas Children’s Hospital website, which contains a memorial page for Henry. The page provides more details on his life and battle with Rett syndrome, a genetic brain disorder without any treatment or cure currently available.

Rett syndrome hinders patients in various ways, including the loss of manual dexterity, difficulty with ambulation, seizures, and decreased intellectual functioning and brain growth.

Henry was born on Sept. 29, 2015 andFall behind some infantdevelopment milestone. after a number of doctor’s appointments and exams including a genetic test, it was discovered he had afaulty MECP2 gene.

“MECP2 mutations cause Rett syndrome, a disorder that typically affects girls after their first birthday, robbing them of learned skills and leaving them with cognitive deficits, loss of speech, and a variety of motor difficulties,” the Hospital page explains.

The Engel family took Henry to the Duncan Neurological Research Institute (Duncan NRI) in 2018 for further help. The Duncan NRI’s Founding Director, Dr. Huda Zoghbi, observed Henry’s mutation carefully.

“Henry was special in so many ways. His loving and endearing smile, and the way he connected with his eyes, stole my heart from the time I met him. His quiet fight against this terrible disease was incredible,” said a doctor who write a tribute to her patient.

Zoghbi stated that Henry had a significant impact on the Duncan NRI team’s future Rett research.

“We will continue to push as hard as possible to develop treatments. This is how we will honor his life,” she continued.

Over the years, Engel has kept the TODAY team updated on his son’s condition. He candidly talks about both the struggles and joys that come with parenting a child who has special needs.

Rett syndrome is a difficult illness for any parent to watch their child go through, but in 2018 Engel wrote an essay exploring the heartbreak and hope that comes with it. He described Henry’s challenges while also emphasizing how grateful he was to have him in his life.

“None of this means we don’t enjoy our time with Henry. I can’t imagine a child who is showered with more love. We gather on our bed several times a day for what we call ‘cuddle parties,’ where we kiss him, rub him, praise him (he loves to hear his name and be praised) and curl his thick, gorgeous hair in our fingers,” he said at the time.

Rett syndrome is a neurological disorder that primarily affects girls. It causes a progressive loss of muscle tone, problems with movement and coordination, and seizures. Rett syndrome is caused by mutations in the MECP2 gene. The symptoms of Rett syndrome usually begin to appear between 6 and 18 months of age. There is no cure for Rett syndrome, but there are treatments that can help improve the quality of life for people with the disorder.

Rett syndrome is a disorder that primarily affects nerve cells in the brain. It is characterized by a loss of muscle control, coordination problems, and seizures. Rett syndrome occurs almost exclusively in girls and is caused by mutations in the MECP2 gene. The symptoms of Rett syndrome typically begin to appear between 6 and 18 months of age. There is no cure for Rett syndrome, but there are treatments that can help improve the quality of life for people with the disorder.

Rett syndrome affects nerve cells in the brain that are responsible for controlling muscle movement. This results in a loss of muscle control and coordination. People with Rett syndrome may also have seizures. The symptoms of Rett syndrome typically begin to appear between 6 and 18 months of age. There is no cure for Rett syndrome, but there are treatments that can help improve the quality of life for people with the disorder.