( CNN ) -- The plight of a 10-year-old Pennsylvania girl who could die within weeks without a lung transplant has sparked a fight for new rules governing organ donations . Tens of thousands of people have signed a petition on Change.org , and a congressman has called on the Obama administration to take quick action . Sarah Murnaghan -- whose story CNN chronicled -- needs new lungs . She 's been in a Philadelphia hospital for months due to the cystic fibrosis that she 's had since birth . She 's at the top of the list for any pediatric lungs that may become available for transplant in her region . She 's been waiting for 18 months . None have come along . But doctors say modified adult lungs could help save her -- and adult lungs become available much more often . That 's where the rules becomes a problem . Kids under age 12 are n't prioritized for adult organs . So Sarah could only get available adult lungs if everyone else waiting for lungs in her region -- no matter how sick they are -- turns them down . Sarah 's mother , Janet Murnaghan , told CNN she was `` shocked '' when she learned the rules a couple of weeks ago . The United Network for Organ Sharing ( UNOS ) manages the nation 's transplant system under contract with the Department of Health and Human Services . The network , established by Congress , is officially called the Organ Procurement and Transplantation Network ( OPTN ) . Lawmaker assails 'tragic unfairness ' Rep. Patrick Meehan , a Republican who represents Sarah 's district , sent a letter Tuesday to Secretary of Health and Human Services Kathleen Sebelius , calling on her to convene a meeting of the network 's leadership immediately `` to address this tragic unfairness and act to give Sarah a chance at life and an adult lung from the next available donor . Sarah 's young life literally hangs in the balance . '' It 's a message echoed on the Change.org petition . `` This policy needs to change , '' it reads . `` The OPTN/UNOS Lung Review Board , a national group of transplant physicians and surgeons , can make an exceptional ruling for Sarah . And they can recommend new policies . '' People posted heartfelt messages along with their signatures . `` Because my daughter had ( cystic fibrosis ) and a double lung transplant . Give this little girl the life she is entitled to ! '' wrote Reyna Kosla . `` She has just as much right to have a transplant as any adult . She could have her whole life if given that chance and for the parents to enjoy what some waiting adults have already experienced , '' wrote Lorraine Husack . Organ network : Breaking the rules could hurt another patient . OPTN issued a statement noting that there is a separate policy for children because the `` biological needs and circumstances of candidates younger than age 12 are different from either adolescent or adult candidates . One key difference is the size and lung capacity of donors and patients among these age ranges . '' Kids younger than age 12 are prioritized for donations from other kids of similar age and size within a 1,000-mile radius . Policies allow `` status adjustments for specifically defined groups of candidates with unique medical circumstances not addressed by the overall policy , '' the statement says . But , it adds , a `` request to adjust the status of a patient under age 12 so that they may be included in the allocation sequence for adolescents and adults is not within the scope of the existing lung allocation policy . OPTN can not create a policy exemption on behalf of an individual patient , since giving an advantage to one patient may unduly disadvantage others . '' The network routinely reviews policies and considers `` public input as well as medical data and experience , '' the statement said . Dr. Stuart Sweet , a board member at UNOS , helped develop the current policies . `` There is no perfect system , '' he told CNN . `` It 's the best we can do right now . '' Sweet said Sarah 's story `` tugs at his heart '' but that if he changed the system for Sarah 's advantage , `` there 's another patient , very likely an adolescent , who gets a disadvantage . '' `` We 've built a system that tries to be as fair to everyone as possible . '' CNN 's Chris Welch , Zain Asher , and Jennifer Bixler contributed to this report .
10-year-old Sarah Murnaghan could die within weeks if she does n't get new lungs . Score: 7 A lawmaker calls on HHS Secretary Sebelius to convene a meeting immediately . The agency managing organ donations and transplants says breaking rules could hurt patients .