SAN DIEGO (AP) — Stan Lee is missing in action at Comic-Con.

A spokesman for the 91-year-old co-creator of superheros such as The Avengers, X-Men and Spider-Man says Lee lost his voice because of laryngitis. He added that Lee is otherwise in good health and is disappointed he’s missing the celebration.

The former Marvel Comics editor-in-chief has been a constant presence at San Diego Comic-Con since the convention launched in the 1970s.

Lee had been scheduled to appear Friday and Saturday to sign autographs and unveil the latest installment of in his Stan Lee’s Kids Universe multimedia project.

Comic-Con is a four-day festival celebrating film, TV, video games, comic books, costumes and other popular arts. It kicked off Thursday and continues through Sunday at the San Diego Convention Center.

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