(WCMH/NBC) — Henry, the 6-year-old son of NBC News Chief Foreign Correspondent Richard Engel, has died after a long battle with Rett Syndrome, a genetic brain disorder that does not have a treatment or cure.

Engel made the announcement Thursday on social media.

“Our beloved son Henry passed away,” read Engel’s tweet. “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.”

As an advocate for other families searching for a cure, Engel also shared a link to Henry’s memorial page on the Texas Children’s Hospital website.

Details on the hospital’s site explained more about the disease and ultimately how the family discovered why Henry was experiencing his symptoms.

“When he was still an infant, his parents noticed that he was not reaching his developmental milestones, and he underwent numerous medical exams to discover the cause,” the page read. “A genetic test ultimately provided the answer: Henry had a mutation in his 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.”

Dr. Huda Zoghbi, Founding Director of the Duncan NRI, who worked with Henry also left a touching memory on the site.

“Henry was special in so many ways,” Zoghbi wrote. “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. What is most amazing, however, is the impact Henry had on so many of us at the Duncan NRI and on our Rett research. We will continue to push as hard as possible to develop treatments. This is how we will honor his life.”

In an additional tweet, Engel echoed how Henry is helping others in the fight against the disease.

“Researchers are making amazing progress using Henry’s cells to help cure RETT Syndrome so others don’t have to endure this terrible disease,” Engel wrote.

Since Henry’s initial diagnosis, Engel and Henry’s mother Mary have shared their family’s journey on NBC’s TODAY show with regular updates to help bring awareness to the childhood disorder.