PHILADELPHIA — Twenty-three-year-old Paul Corby has a bad heart and a flawed mind.

The question before doctors now is whether his autism is severe enough to make him a bad candidate for a heart transplant.

Doctors at the Hospital of the University of Pennsylvania have said they are, according to Paul’s mother, Karen. She disagrees and is using an online petition and the support of a network of autism advocates to make her case. Karen Corby says she was “stunned” by Penn’s decision, then inspired by another family’s successful fight with Children’s Hospital of Philadelphia over a similar decision.

“I guess they thought we would accept it and just wait for the inevitable,” said Corby, of Pottsville, Pa. She said she has not been told how long her son, who has a heart condition called left ventricular noncompaction, might live without a transplant.

Paul Corby initially took the decision well, but has since grown so depressed that his mother worries about how he’d react to another rejection.

“At first he was OK with it because he thought, ‘At least I don’t have to go through that surgery,’” his mother said, “and then he thought, ‘Why not? Why don’t they like me?’”

Paul Corby’s situation is a window into the complex decisions that patients and doctors face when vital organs begin to fail. Organ transplantation is one of the few areas of modern medicine with overt and unavoidable rationing. There simply are not enough donated organs to go around, so doctors must make life-and-death choices. Nationally, 331 people died while waiting for heart transplants last year.

Karen Corby released a letter she received from Penn cardiologist Susan Brozena in June 2011. In it, Brozena said that she recommended against Paul Corby’s getting a transplant “given his psychiatric issues, autism, the complexity of the process, multiple procedures and the unknown and unpredictable effect of steroids on behavior.”

Corby said her son — who is diagnosed with Pervasive Developmental Disorder Not Otherwise Specified — is high functioning and spends his days playing video games and writing the sequel to his pre-teen, self-published novel, Isaac the Runner.

Citing privacy rules, the Penn health system said it could not comment on Paul Corby’s case. It released a written statement that said the transplant program reviews “all aspects” of a patient’s condition, including his health status and post-transplant prognosis, and other health problems that could affect transplant success along with the interaction of drugs he takes and those he’ll need after the transplant.