For the parents of Sarah Murnaghan, 10, who is dying of cystic fibrosis at Children's Hospital of Philadelphia, the bottom line seems heartbreakingly simple: She should be offered the first suitable lungs that become available, whether the donor is a child or adult.

Instead, the Newtown Square couple say, organ-donation rules require adult lungs to be offered first to adults who are in less dire need than Sarah.

There is nothing simple about this case or the rules governing transplants. That's why Sarah's transplant doctors at Children's Hospital asked for advice from the St. Louis pulmonologist who helped develop the national pediatric-transplantation rules.

"It's really sad that this child has waited" for 18 months, said Stuart Sweet, director of the lung-transplant program at St. Louis Children's Hospital. "But the issue here is really about how we designed this system to try to make it fair for everyone waiting for lungs. There are ways of working through this that don't involve breaking the rules."

Sarah's mother, Janet, who on Friday launched a last-resort public-relations blitz, disagrees: "The law is, in my view, age discrimination. I don't know if this is too late to make a difference for Sarah. But we'll keep fighting it."

Sarah's situation was unusual from the start, her mother said. Her cystic fibrosis - a disease in which sticky mucus clogs the lungs - was diagnosed relatively late, at 18 months old. By then, she had severe lung damage. Her lung function declined, despite the drugs and therapies that enable most CF patients to remain fairly healthy into their teens or beyond.

Eighteen months ago, Sarah qualified for the lung-transplant waiting list in the Philadelphia region, coordinated by the Gift of Life Donor Program. Since February, she has been at Children's, where she needs a modified ventilator to breathe.

"Now, her carbon dioxide is building," her mother said. "She has only a week or two before she will lose her battle."

The family's perception of unfairness is rooted in the complexities of the national Organ Procurement and Transplantation Network.

The lung-allocation system was overhauled in 2004 and further modified in 2008. Since then, far fewer people of all ages on the waiting list have died, Sweet said.

Lungs are allocated by age groups - under 12, 12 to 17, and 18 and older - based on severity of medical need. However, the classification systems are different for children under 11 and for older patients.

Because relatively few children die each year (a good thing), there are few pediatric lungs available for transplant (a bad thing). Last year, only 20 lungs were donated from children under 12, compared to about 1,500 from adults.

That's why the Murnaghans believe it is unfair that adult lungs must be offered to all wait-listed adults before the organs are offered to adolescents or children.

"She could have lobar transplant, taking 40 percent of an adult lung," her mother said. "The outcomes are very good."

But the picture is more complicated, Sweet said.

Though the supply of pediatric lungs is small, so is the demand. Unlike adults, children can receive lungs from virtually anywhere in the country. Sarah would be the first to be offered lungs within a 1,000-mile radius.

"She has virtually no competition in her age group," Sweet said. "And you have to look at fairness from both sides. While children can use adult lungs, adults generally can't use pediatric organs."

She may also be offered adolescent lungs; 144 became available last year.

The Murnaghans said Sarah's doctors asked a national Lung Review Board to bend the rules and let Sarah receive the next available adult lungs. The appeal was denied.

However, Sweet said, such an appeal could be made personally to an adult transplant center, such as the University of Pennsylvania.

"There is nothing that says you can't reach out and ask," he said. "There are circumstances where we [in St. Louis] make a judgment and recognize that . . . the organ we've been offered shouldn't go to the patient at our center. It's a balancing act. We don't want to deprive a more urgent patient of a chance."

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