Legendary comic book creator Stan Lee has canceled his appearance at Salt Lake City Comic Con's FanX due to undisclosed "health reasons." In a statement on their Facebook page, organizers wrote, "After a second visit to the doctor this morning, he was advised to rest and recuperate rather than risk getting worse." They continued to say that, although they are disappointed, they "wish him a speedy recovery."

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Lee was scheduled for a panel and autograph session with fans. Those who have bought autographs or photo ops with the legendary creator will be able to convert them to a voucher with a 10% premium, save them for the next convention, or get a partial or full refund.

Lee, who turned 94 in December, also had to abruptly cancel an appearance at Big Apple Comic Con last weekend, likely due to the same health problem. In recent years, Lee has had to call off other appearances due to this health. After dropping two appearances in Ohio in 2012, Lee revealed that he'd had a pacemaker implanted. Lee was also rushed to hospital in 2015, though he was able to attend the red-carpet premiere of "Ant-Man," which happened the next day.

Lee has been slowing himself down in recent years, having already made his final convention appearances in Canada and Europe. However, he still keeps an incredibly active schedule. Back in 2016, he shot four cameos in one day, and he just threw out the first pitch at a Texas Rangers game.

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Lee joined Timely Comics, which would later become Marvel Comics, in 1939. Along with Jack Kirby and Steve Ditko, Lee helped create many of Marvel's most iconic superheroes, including the Fantastic Four, the X-Men, Spider-Man, the Hulk and many more.

Salt Lake City Comic Con is held on March 17 and 18.