A five-year-old boy with a medical implant just got a big fist bump from one of Marvel's most famous Avengers.

Marvel Comics recently included five-year-old Max Levy in its "Invincible Iron Man" comic book, in a nod to the child's battle with hemophilia A. In the comic book cameo, "Iron Max" is shown meeting his favourite superhero, Iron Man. The comic shows Max trying on the Iron Man armour, and getting some words of encouragement from Tony Stark, Iron Man's billionaire alter ego.

The comic book appearance comes after Max's father, Dan Levy, shared his son's story with Marvel through social media, using the hashtag #IronMax. Levy has also used the hashtag to raise money for hemophilia research at the Children's Hospital of Philadelphia, where Max is treated.

Max was diagnosed with hemophilia A at the age of three – a condition that required him to have a portable catheter device implanted in his chest, to help regulate his blood flow. Max's condition causes his blood to clot very slowly, meaning his cuts bleed for a long time before they scab over.

According to Levy's blog, he told Max at the time of the surgery that the implant would make him just like Iron Man – a notion that Max quickly embraced.

In the comics, Tony Stark has a super-powerful battery implanted in his chest, which keeps shards of shrapnel from migrating to his heart and killing him. The battery also doubles as a power source for his Iron Man armour.

"You get to be Iron Man, buddy," Levy recalled telling his son, in a post on his blog.

On the day of Max's surgery to get the device implanted, Levy tweeted at Marvel using the #IronMax hashtag, and Marvel responded. On June 25, 2014, the Iron Man movie account tweeted to Max, saying: "We're gonna be two of a kind." That same day, Brian Michael Bendis, writer of the "Invincible Iron Man" comic, vowed to put Max in an upcoming issue.

Bendis is heavily involved in various comic book and TV superhero properties, including Netflix's "Jessica Jones," which he co-created several years ago.

As a result, it took him more than a year to follow up on his promise, Levy said. But in September of last year, Bendis finally requested photos of Max and his dad, with the promise that they would "meet Iron Man in Issue 4."

The comic, written by Bendis and drawn by Dave Marquez, was released on Dec. 2, 2015.

In the comic introduction, Bendis wrote: "Since heroes belong in comics, we couldn't resist giving Max a cameo in ours!"

Bendis also refers to the Levy family's charitable initiative, called Hearts 4 Hemophilia, which sells calendars to raise money for hemophilia research at the Children's Hospital of Philadelphia.

The fundraiser has collected more than US$8,000 in donations.

Iron Max Levy