Phaneron

Question: It's stated a couple times in the movie that Arnie could die at any moment. Pardon my ignorance, but why exactly is this? Is there something about his condition that makes him highly susceptible to dropping dead, or is it a matter of his behavioral impulses (such as climbing the water tower) that put him at a high risk of dying in an accident?

Phaneron

Answer: In the beginning, Gilbert explains that the doctors said Arnie will only live till 10 years old, and that he is well past that, so he "could go at any time."

Chosen answer: It's because of his often reckless behavior; it's never implied within the film that his unique condition has anything to do the likelihood that he could "go at any time."

zendaddy621