NEW YORK (FOX 5 NEWS) - Peek into the Moons' backyard in Westchester County, New York, you'll see three happy children enjoying every ounce of this warm September day. What you can't see is that behind Jacob Moon's bright eyes and warm smile lingers a devastating illness that will, undoubtedly, claim his life.
"Essentially, Jacob lacks an enzyme that breaks down sugars," Bill Moon, Jacob's father, said. "And those sugars are stored in his brain, eventually becoming toxic."
That illness is Sanfilippo syndrome, a neurologically degenerative, fatal disease that affects one in 70,000 kids. The toxins cause loss of speech, hearing, and motor skills. Jacob also exhibits extreme hyperactivity and vocal stimming.
"Sanfilippo is often called childhood Alzheimer's," Christine Moon, Jacob's mother, said. "He truly has forgotten how to do things. He's forgotten people."
A birthday video from 2016 shows Jacob had no problem singing along. But just one year later, as hard as he tries he can't find the words.
"I'm lucky if I can get two words from him a day now," Bill said.
Sanfilippo has no cure and no treatment. Currently, only one clinical trial is underway in the United States. The research shows that kids don't often live past their teenage years. The disease so rare that Sanfilippo kids are often initially misdiagnosed with autism.
"We do find ourselves having to teach doctors about it," Christine said.
This is an issue deeply personal for the moons, especially, their children.
"I don't like it when people stare at him, which happens all the time," Ella Moon, Jacob's sister, said.
The 10-year-old said her brother has taught her how to be kind to others who may have special needs. Like her parents, she chooses to focus on the here and now and remains optimistic about the days ahead.
"Most of the times I just try to see what's still there in Jacob," Ella said.