It was hard enough for Karen Corby to hear that her autistic son would need a heart transplant to survive, but it was even harder to take the news that doctors wouldn't give him one.

"I was numb at first," Corby, of Pottsville, Pa., told ABCNews.com, remembering the phone call from Paul's cardiologist when she found out he wouldn't be placed on the transplant list. "Before she hung up, she told me to have a nice day."

Her son Paul, 23, has a left ventricle that didn't close after he was born, so his heart doesn't pump the right amount of blood. The Corbys found out in 2008, and were told it was time for a transplant in 2011.