Updated

A second family has stepped forward in the public fight to change a donor-organ policy that places sick children younger than 12 years of age at the bottom of the adult transplant list, regardless of the severity of their illness.

The mother of Javier Acosta, 11, who suffers from cystic fibrosis and needs a lung transplant, urged policymakers on Saturday to adopt new rules to make a life-saving adult lung more readily available to her gravely ill son.

"If Javier does not receive a transplant, he will die," Milagros Martinez said during a news conference in Philadelphia. "I say that's unfair because of a policy. It shouldn't be that way."

The family of Sarah Murnaghan, 10, who like Javier is suffering from cystic fibrosis, is also publicly calling for a change in transplant list policies administered by the Organ Transplant and Procurement Network.

The Murnaghan family efforts have garnered national media attention and scrutiny of lawmakers on Capitol Hill, some of whom have called on U.S. Health and Human Services Secretary Kathleen Sebelius to intervene.

Last week, U.S. District Judge Michael Baylson granted the two families a temporary court order barring enforcement of a policy that places children under age 12 at the bottom of the adult lung transplant list, regardless of their illness.

The Murnaghan and Acosta children are both awaiting lung transplants at the Children's Hospital of Philadelphia. While each is eligible for donor lungs from children, those are rare.

The lawsuits have led some to voice concerns that adding children to adult transplant rosters could end up pushing deserving older patients farther down the list.

But Stephen Harvey, a lawyer for both families, said his clients want a policy change based on patients' relative conditions, not their ages.

"We're seeking that the system allocate a lung to Javier based on the severity of his condition," Harvey said. "So if there's an adult who's more severe than him, that adult gets the lung. We're not asking to jump to the front of the line."

The executive committee of the Organ Transplant Network is due to meet on Monday, at which time it could announce a review of the transplant rules. Failing that, a hearing to review the restraining order is scheduled for June 14 before Judge Baylson.

It was unclear how many children would be affected by a shift in rules. Harvey said there are 16 children aged from 5 to 10 currently seeking lung transplants, and that 23 such procedures were performed on children in 2011.