Last spring, Henry DeYoung proudly displayed a poster about his award-winning computer security research at Carnegie Mellon University.

He didn't actually display the poster, to be technical about it. That would have required him to stand and place the placard on an easel, and he couldn't do either of those things. Henry has spinal muscular atrophy, a muscle-weakening disorder that forces him to use a wheelchair, limits how much he can use his hands, and requires him to wear a breathing tube to help with his respiration.

None of that, however, kept the 23-year-old from being named Carnegie Mellon's top undergraduate computer science student last spring, nor has it kept him from enrolling in the school's Ph.D. program this fall.

"Actually," said his academic adviser, Dr. Frank Pfenning, "he wasn't just the best; he was head and shoulders above everybody else."

And there was one other remarkable thing, the professor said. Henry's younger brother Andrew, 21, is also a student at Carnegie Mellon, and is just as brilliant, and has exactly the same form of muscular dystrophy.

In the Franklin Regional School District, where the brothers grew up, they were already local celebrities before enrolling at Carnegie Mellon.

Henry left high school in 2003 with a top score on seven Advanced Placement tests, which gave him about a year's worth of college credit heading into his freshman year.

Andrew is carrying a 4.0 grade-point average at Carnegie Mellon as a chemistry major, and left high school in 2005 with his own set of seven top AP exam scores.

Even more remarkable than their academic distinction is the way that their parents, David and Joan DeYoung, and a small army of friends, church members and nurses, have made it possible for the young men to survive and prosper.

It has been a long and sometimes perilous journey, and one they hope will continue indefinitely.

When Henry was born, the DeYoungs didn't notice anything unusual at first, except that he was mentally precocious. He walked at the expected age and could use his hands normally.

"There were a couple things in retrospect I realize weren't right," said David DeYoung, a research engineer for Alcoa Inc., "but at the time I didn't notice, like how Henry would fall in the back yard and not be able to get up. 'I'm stuck, I'm stuck,' he'd say."

At the suggestion of a neighbor, Joan DeYoung took Henry to the pediatrician, who noticed a problem immediately.

"This pediatrician, who was known for not having a bedside manner, he just looked at me and he said, 'He has muscular dystrophy,' and he immediately picked up the phone and called Children's Hospital to make an appointment with a specialist. I remember being stunned and going to the store afterward, and thinking, 'What did he say Henry had?' I wasn't even sure what muscular dystrophy was.

"But looking back on it," Mrs. De- Young said, "it all worked out, because some families get misdiagnosed for years. I think it was a curious blessing."

When she and her husband got the news about Henry, she already was pregnant with Andrew.

Spinal muscular atrophy is an autosomal recessive disorder, which means both parents are carriers, but are not affected themselves.

For such parents, there is a one in four chance that their children will be unaffected, a two in four chance that the children will also be carriers and just a one in four chance that they will acquire the muscle-weakening disorder.

Though it is not nearly as well known as the Duchenne muscular dystrophy often featured on Jerry Lewis' Labor Day telethons, SMA is almost as common, affecting 1 in 10,000 children, compared to 1 in 6,000 for Duchenne.

It afflicts the body's motor neurons, causing curvature of the spine, a progressive loss of use in arms and legs, and breathing problems. When children or adults with SMA die, it is usually from lung infections, because they are not able to cough normally and clear their lungs of germs.

While research is moving forward to find a treatment or even someday a cure for the disorder, no effective therapy is currently available.

When the boys were younger, David DeYoung said, he used to read the Muscular Dystrophy Association magazine, "and they'd say they were investing money for a cure, but each year it was the same stuff, and eventually, I thought, 'I can't back all my hope on that because it's likely not to happen in my lifetime.'

"Friends would always say, 'They'll come up with something,' but I thought, it's easy to comfort someone by saying that, but there are a lot of things in this world that aren't curable."

Better, he and Mrs. DeYoung thought, to invest themselves in making each day as productive as possible for their sons.

In an oddly poignant way, they had a head start on being able to do that.

Dr. DeYoung's father, for whom Henry is named, died of another neuromuscular disease, amyotrophic lateral sclerosis, also known as Lou Gehrig's disease.

He already knew from his father's experience in a wheelchair that removing the carpeting from floors and having rooms big enough in which to maneuver were important.

To help his mother out after his father died, Dr. DeYoung also had bought his dad's van, which was equipped with a wheelchair lift, never thinking he would need it for his own children.

When Henry was diagnosed, the DeYoungs were living in a two-story home in Plum, and they knew that wouldn't work. The best thing would be to design a one-story home for themselves, they knew, but Dr. DeYoung never thought he'd be able to afford that.

But then he was able to find a relatively cheap piece of land on Hills Church Road in Murrysville, and using many of his own ideas, helped design the one story-residence the boys grew up in.

It has no carpeting, wide hallways and doorways to accommodate the wheelchairs and a roll-in shower in Henry's and Andrew's bedroom, with a shower chair. Dr. DeYoung even made sure the windows were set low in the walls, "because in the old house, the boys were never able to see out."

Although Henry and Andrew have the same disorder, it has affected them in different ways.

While Henry learned to walk before losing his mobility, Andrew never even learned to crawl, and has always had less muscle tone than his older brother. But Henry for some reason has been more susceptible to lung infections -- a problem that has decreased as they've grown older and are exposed to germs less often in public places.

As they grew up, they had the same kind of rivalries other brothers do, but they also had to rely on each other, their parents said.

Dr. DeYoung rigged up their video game system so that each boy had a controller to manipulate the same character, so that when they played Mario Brothers, for instance, "Henry would make Mario run and Andrew would make him jump," Mrs. DeYoung said,

And then if Mario died, Dr. DeYoung added, they'd start arguing. "'He got killed because you didn't do it right,' they'd say."

Because they needed help not only with daily living tasks but with completing their homework, Mrs. DeYoung said, they became acutely aware of each others' needs and schedules.

"They were always coordinating," she said, "so it would be like, if mom's writing Henry's seventh grade algebra, then she can help me later with my Little House on the Prairie project."

In a technical sense, the young men may already have outlived the typical life expectancy of those with SMA, but it's not an issue either they or their parents dwell on.

Mrs. DeYoung always remembers what one neurologist said when Henry was first diagnosed. "Most of these kids die before they're two -- but save for college."

Dr. Geoffrey Kurland, the pulmonary specialist who took care of Henry and Andrew until recently, said the whole DeYoung family are heroes to him, and added:

"I don't know how long Henry and Andrew are going to be here -- I hope for a good long time."

Andrew DeYoung, who feels he has been blessed by the family he was born into, has this philosophy about the matter:

"I think one's circumstances affect one's life, and I think it's helpful if I and others remember that, and know that really, circumstances are just circumstances, not necessarily bad," he wrote in an e-mail.

"In other words, we all need to remember that every person has value, not because of what we do, but just because we are. And it doesn't matter whether one is president of the United States or is one of the dozens of sick children waiting right now at Children's Hospital for a transplant -- I think that if we all remembered that we all have value, life would be a bit more pleasant, and less goal-oriented."