When Marvel's Ultimate imprint started, it promised a completely fresh spin on existing heroes and a world not too far removed from our own. Ultimate Iron Man was certainly one of those things.
In 2005, Orson Scott Card found time in-between writing sci-fi novels to create an origin story for this universe's version of Tony Stark.
The character had already appeared as part of the Ultimates (The Ultimate Universe version of the Avengers) and was established as being a billionaire alcoholic with a brain tumour, trying to put what little time he has left to good use as a hero. This is information that Card completely ignored.
His version of Iron Man was a super-genius because his entire body was made of brain tissue, which also somehow gave him superhuman healing, allowing him to regrow lost limbs and even survive getting shot in the head. His first "armour" was a special protective coating (because his skin was so sensitive that even air hurt it) that turned his skin blue and could be washed off with soap.
You would think the other Ultimates would've mentioned all of that at some point but apparently Captain America and Nick Fury were just too polite to ever bring it up.
Thankfully, the whole miniseries was later retconned into being a cartoon show within the Ultimate Universe.