No child had ever received a transplant of a single hand, let alone two. Only about 60 people worldwide - including Penn's first case, a young woman, in 2011 - have undergone upper-extremity transplants since the first one in France in 1998, according to the international registry.
These complex "composite" tissue transplants - which involve reattaching blood vessels, bones, nerves, muscles, and skin - remain rare because, unlike major organ replacements, they are not lifesaving. Yet patients must take immune-suppressing drugs for the rest of their lives to prevent rejection, raising their risks of infection, some cancers, and other side effects.
Zion was uniquely suitable because he was already taking antirejection drugs to protect his kidney transplant.
The backstory: At age 2, a life-threatening bloodstream infection required the amputation of his hands and feet and ruined his kidneys. At age 4, after two years on dialysis, he received a kidney from his mother.
About two years ago, she took him to Shriners Hospital for Children in Philadelphia, which specializes in caring for kids with prosthetics like those he wears on his lower legs. There she learned about Penn's hand-transplant program.
"The doctor at Shriners thought Zion would be a perfect candidate," recalled his mother, a nursing student at Baltimore Community College. (She declined to discuss where Zion was treated for the life-threatening infection, but public records show litigation involving Sinai Hospital of Baltimore and others.)
Zion's precocious self-awareness and resilience also impressed the transplant team.
On a documentary video made by the team, Zion says of his stumps: "I wasn't always like this. When I was 2, I had to get my hands cut off."
Of school, the second grader says: "I think some of my classmates don't mean to say mean things to me, but it just slips out. Everybody has their own way of thinking about things."
Anticipating the transplant, he says: "When I get these hands, I will be proud of what hands I get. And if it gets messed up . . . I don't care because I have my family."
His mother says he took the transplant surgery in stride. "This is just another hurdle that he jumps. He's so amazing."
Levin, the transplant leader, called Zion "one of the most remarkable youngsters I've ever met."
"His maturity is way beyond his age, as is his insight and sensitivity," Levin said. "He's brilliant, not just smart. And his stoicism has been remarkable. I've never seen him cry, complain of pain, or be withdrawn."
In April, Zion was put on a waiting list for hands, to be obtained through Gift of Life, the region's organ and tissue transplant network.
Zion and his family were warned that the wait might be a year or two. Federal organ-sharing data showed that only a tiny number of children of the appropriate race, age, and sex become donors each year.
But just three months after he was listed, Zion underwent the 11-hour surgery, an overnight marathon involving two dozen surgeons, nurses, and anesthesiologists. The process required four separate surgical teams, two for the donor hands and two for Zion.
Steel plates and screws were used to connect the forearm bones, then the arteries and veins were sewn using thread thinner than a human hair. With blood flow reestablished, each muscle and tendon was reattached, followed by the nerves.
How does Zion feel about the donor?
"Mixed emotions," he said of the loss that made his gain possible.
Zion faces many months of physical rehabilitation. While in the hospital, he has been fitted with a series of custom-molded plastic splints that protect his wrist and fingers, while allowing therapists to help him learn to use his new hands.
"By September, the splint will be less bulky and cumbersome, and his wrist should be free," said Children's occupational therapist Kelly Ferry.
Sensation is another issue. The nerve regeneration that restores feeling can take up to two years.
Meanwhile, the hands will grow with him, as the growth plates produce new bone and tissue. Already, Ray noticed, his fingernails need clipping.
Zion seems up for the challenges. On Monday, he shook hands, scratched his face, held a book with help from his mother, all while being interviewed.
Does he have a favorite caregiver at Children's?
"I like everybody," he said.