Joe Eitl’s family always knew the day would come when he might need a heart transplant.

Joe, 37, was born with Down syndrome and cardiac defects; he has a hole in his heart and only one ventricle instead of the normal two. When he was a toddler, he underwent the first of many surgeries to improve his condition. Since then, he has undergone other open-heart procedures and catheterizations and has been treated with medications. But these have been stopgap measures, not cures, said his mother, Peg Eitl.

“They’ve all been palliative, short-term, buy-him-some-time sort of thing. He’s outlived his life expectancy,” she said. “He’s been at the last-rites stage several times in his life, but he’s always bounced back.”

And he’s created a joyful life in the process. In fact, he’s become a bit of a celebrity in his corner of Montgomery County, where he lives in Skippack with his parents, Peg and Craig Eitl, both 59. (His sister, Lacey, 30, lives in Lafayette Hill, and brother Jason, 34, is in Collegeville.)

A small man with a big spirit — “Mr. Personality,” Peg calls him — Joe has always had lots of friends, is a Special Olympics multisport athlete, and has fronted a local rock band with his “soul man” moves. The Collegeville Italian Bakery even named a sandwich in his honor, The Joey: low-fat cheese and low-salt ham on a dinner roll.

But a year ago, Joe went into heart failure. He was weak and retaining a lot of fluid. His heart problem caused stress to his organs, including damage to his liver. His parents started the long, complicated process of having him evaluated for a possible heart and liver transplant. Even ever-ebullient Joe some days found it hard to muster any energy.

So Peg started posting on Facebook about his medical odyssey. Friends and family members posted Facebook requests for people to send Joe cards and notes of support, because he loves receiving snail mail. They included his mailing address, should anyone feel moved to drop him a line. Others then shared the post, which led to even more shares.

And the mail started coming. And coming. And coming.

An elementary school organized a card-writing drive for Joe. A high school football team “adopted” Joe, and showered him with notes and letters.

He has received commemorative coins from American Legion posts and police associations, as well as correspondence from the Eagles, the Phillies, and the Flyers.

One greeting came all the way from England. Another card, posted from out West, came with a hand-drawn picture from a little girl named Becca and a note that read, “You don’t know us, but we wanted you to know our family is praying for you.”

Some senders have become such regulars, the Eitls now recognize the handwriting.

Patrick McNamee, 63, of Orange Park, Fla., has been sending Joe cards at least once a week since reading a Facebook post almost a year ago.

“It’s the right thing to do,” said McNamee, a retired teacher and family acquaintance.

Marsi Fluehr, 69, of Ambler, also a retired teacher, met the Eitls 20 years ago when her daughter and their daughter were playing AAU basketball together.

“Joe was our No. 1 supporter,” said Fluehr, who often encloses a dollar or sweet in the cards she sends Joe — “something to make him smile.”

And, of course, Joe has had the support of his own close pals. At the top of that list is Mark Graham, 35, his best friend since they met in special-education classes at Gladwyne Elementary School. They FaceTime each other every day.

“I would be happy for him to get his new heart and get better,” said Mark, who lives in Gwynedd Valley. “He’s always been my buddy.”

The Eitls couldn’t count all the mail Joe has received, even if they tried.

“We have thousands of cards — tens of thousands, buckets of them,” marveled Peg. “We tried to keep track of what states we’d heard from and it got hard to manage. We got cards from Alaska and Utah. We don’t know people in Alaska and Utah.”

The Eitls finally took mercy on their Skippack mail carrier and got Joe his own post office box (Joe Eitl, P.O. Box 650, Skippack, PA 19474).

People knowledgeable about the transplant process told the Eitls early on that emotional and community support are taken into account by transplant review panels when they decide if a patient is a viable candidate for the surgery. There is no doubt about Joe’s support, or what it has meant to him.

“Whether he gets a transplant or not, we really don’t know,” said Peg, who works in health-care sales, “but what we do know is during some of the really difficult times, the cards, the letters, and the gifts from strangers have literally made a difference between a day he didn’t want to get out of bed and a day he bounced out of bed. It’s been awesome.”

Getting a transplant remains far from certain for someone who entered the process as sick as Joe. He is currently under the care of doctors with the Hospital of the University of Pennsylvania and the Vanderbilt University Medical Center in Nashville.

Jonathan Menachem, Vanderbilt’s director of Advanced Congenital Cardiac Therapies, said Joe was turned down for a transplant because the transplant committee was concerned he would not survive the procedure. But that doesn’t mean there is no hope.

“During his transplant evaluation he was deemed not a candidate due to [other] organ dysfunction and the associated frailty he developed as a result of his heart disease,” Menachem said. “That being said, we’re very involved in his care and hope that we can improve aspects of his candidacy that would make his likelihood of success higher.”

That care currently includes new medications that seem to be bringing some improvement, the doctor said.

Joe’s father, Craig, has been leading his son through a home exercise regimen that includes weights to gently build up his strength.

“When we went down to Tennessee to get the evaluation, they said he’s just too frail,” said Craig, a retired contractor. “We came home and started working out.”

When it comes to attitude, the Eitls are taking their cues from Joe.

“He’s got an amazing spirit, and he does believe he’s getting a second heart, and we have no choice but to believe with him,” Peg said. “We approach every day like the gift that it is. We’re just grateful that he has as many good days as bad days. Part of what makes for good days is the love and support we get from family, friends — and even strangers.”

Joe, a man of few words, puts it best.

“I do love the people that send me the cards,” he said. And he knows what he wants to do with his new heart: “Go back to sports!”

Bocci, basketball, bowling, floor hockey — watch out, Special Olympics: Joe is primed to get back to playing them all.

He has travel plans as well. He wants to take his good buddy Mark — and that new heart — to Dave & Buster’s and on a Disney cruise.

Oh, and Joe has something to say to those nice folks who sent him all that mail:

“Thank you!”