A 4-year-old Roxborough boy is a 1-in-170,000 child. His parents are racing against the clock to save him

Emily Lieber is the kind of teacher you remember: Patient and fun, energetic and creative. Many of the kindergartners and first graders she has taught at Meredith Elementary School in South Philadelphia have a love for her that borders on reverence.

"She's magical," said Christina Pascucci, Meredith's Home and School Association president and a grateful former parent.

That's particularly remarkable given the things weighing on Lieber and her family.

Lieber and her husband, Steve, have two spunky boys: Jonathan, almost 7, and Ethan, 4. Jonathan is healthy. Ethan has a rare genetic disorder that will, by the time he is 5, likely begin robbing him of his ability to walk, talk, and recognize his family. Unchecked, it will kill him by the time he's a teenager.

"Teaching is a great distraction," Lieber said. "But sometimes, it's hard not to look at the kids and think, 'Well, my kid is never going to have this experience.'"

Ethan is a 1-in-170,000 child suffering from a condition so rare that just 500 boys in the United States share the diagnosis: Hunter syndrome.

Most of the time, Emily can get through the explain-Hunter-to-a-new-person spiel without crying.

Ethan was born healthy, just like his big brother. The path to a Hunter diagnosis began when he was 18 months old.

"He wasn't talking well," said Emily. "He wanted to verbalize, but it didn't make sense."

He would gesture and grunt, but it was clear that he wasn't understanding what his parents were saying to him, and they couldn't understand what he was trying to communicate, either.

A visit to an audiologist quickly led to a diagnosis of bilateral hearing loss. In most cases, such a condition in a young child tells doctors something else is at work, and genetic testing revealed a diagnosis that Emily and Steve struggled to pronounce or comprehend at first — Mucopolysaccharidosis Type II, or Hunter syndrome, a genetic disorder that affects boys almost exclusively. Emily is a carrier; Jonathan is unaffected.

Emily is good at explaining complicated things succinctly. That's the first grade teacher in her. The way she describes it, Ethan's body can't make the enzyme that serves as the trash truck of the body, removing cellular waste that, in Hunter kids, builds up, eventually affecting every system in his body — "permanent and progressive damage," the Mayo Clinic terms it.

Think of the TV show Hoarders, said Kim L. McBride, a clinical and biomedical geneticist at Nationwide Children's Hospital in Columbus, Ohio.

With Hunter syndrome, "things build up and build up and build up until your house becomes uninhabitable," McBride said. "The cells are not able to function."

Hunter syndrome will eventually cause neurological, cardiac and respiratory problems. In some children, it mimics an autism spectrum disorder. Ethan has some cognitive and behavioral issues. He has delayed speech. For a time, he was prone to self-injury. He lacks coping mechanisms and is more susceptible to illness than other children.

School — Ethan attends the Clarke School for deaf and hard-of-hearing children in Germantown — has helped him advance tremendously, smoothing out his frustrations over not being able to verbalize or understand what people are saying to him. But Hunter syndrome always hovers in the background, even as a smiling preschooler in Ninja Turtle pajamas gleefully drops marbles into a maze with his dad at home in Roxborough.

"We're getting to that point where we see signs of it," said Emily. "He's happy and jovial now, but it's all going to change in a few years."

Ethan's medical, behavioral and educational needs are complicated; the family wanted a parent at home full-time to manage. Steve, who works for a facilities maintenance company, was able to switch shifts to work weekends; Emily kept her teaching job, which offers good health insurance and, through the Meredith community, a strong support network for the Liebers.

"Even when her son was diagnosed, she never lost her spirit with our children," said Pascucci, the Meredith parent. "She came in and smiled and made sure that our babies had everything they needed."

Shortly after his diagnosis, Ethan began weekly four-hour infusions of Elaprase, a synthetic hormone that mimics, to a degree, the one his body is unable to make. It has slowed some of the symptoms, but can't ward off the coming devastating neurological issues, compared by some experts to Alzheimer's disease.

"We try to live each day mindfully. We're not ones to wallow. We try to find the good when we can," said Emily Lieber. "We try to make every day a fun day."

Advances have been made in the 100 years since Hunter syndrome was identified by a Canadian doctor — the infusion Ethan and other Hunter patients receive weekly was only approved by the Food and Drug Administration in 2006.

But even when Case Hogan was diagnosed with Hunter syndrome in 2009 at age 2, doctors in Nashville talked to his parents, Melissa and Chris, about palliative care.

"They told us, 'Your child will deteriorate and die,'" Melissa Hogan said. "There were no options."

The next year, Case was accepted into a clinical trial of a drug that is injected into his brain; it has slowed the disease's progression somewhat. Melissa Hogan, a lawyer by training, and three other Hunter moms initiated the research themselves, she said, because nothing existed.

"We called researchers and said, 'We know you did this in a similar disease, could you do this for Hunter syndrome? We wanted to save our own kids," Hogan said.

As with other "orphan diseases" — rare conditions that affect fewer than 200,000 people nationwide — the research being done to treat Hunter syndrome is being driven not by pharmaceutical companies but by the Hogans, Liebers, and the 2,000 affected families around the world.

McBride, the Nationwide Children's researcher, said a gene therapy approved by the FDA for clinical trial could halt the progression of the disease. Hunter families across the country are fundraising to come up with the $750,000 needed to run the trial, which should begin a few months after the funds are raised. To date, they have raised just over $28,000 of the needed funds.

Many Hunter patients have already deteriorated to the point where the new drug can't help them. But Hogan and the Liebers hold out hope.

"We've already lost generations of kids," said Hogan. "We need to save others."

There are risks, of course. Even when the money is raised, only nine children will be selected for the trial, and there's no guarantee that one of them will be Ethan. The entrance criteria for the trial won't be known until the trial is live, but patients who are too far gone won't be eligible, and the remaining children will likely have to meet certain medical and neurological criteria.

But Emily looks at her cheerful boy and smiles.

"Nothing's going to go forward," she said, "unless we try."