#so many beautiful possibilites

Consider- HIV+ Tony.

The AIDS epidemic began when he was still not with Pep and therefore probably having fun sleeping around. And since at least in my headcanon Tony is pan, and therefore at high risk, it’s very plausible for him to have caught it. His wealth gives him a plausible way to have survived it. (Note: I’d probably set this later than ‘87 but earlier than ‘90 so that the public at large would not yet be wanting to help but after zidovudine was developed.)

Afterwards, he would likely become a face for those who are fighting it. Create a new section of Stark Medical to specifically work on HIV, because almost everyone else with the resources is busy examining their own rectums. Not the best idea when a deadly disease is roaming about.

Later, this makes his getting the reactor fascinating. Now he’s doubly immunocompromised. (source for continued compromisaition on a lower level after treatment, specifically in the gut: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2777614/ ). He’d need to make a special suit for visiting kids in hospitals so that their germs wouldn’t get in and make him fall seriously ill. He might actually go to medical like he’s supposed to because he can’t afford for an infection to start. His workshop and penthouse are likely crammed with various kinds of disinfecting medicines, lights, and filters. 

It probably kills him that he can’t go and comfort his friends when they’re ill. He can’t visit Pepper when she catches a stomach bug, so he sends her soup and tears a chunk out of the sleazy businessmen she would have had to deal with in her place. 

He can’t eat any food from the shitty places Clint and Steve love, their lack of good health procedures makes it go from dicey to a serious risk.

Also, HIV can lead to nervous system issues, something I just learned about. (source: https://www.summitmedicalgroup.com/library/adult_health/aha_aids_nervous_system_complications/ ) Since nerves have trouble repairing themselves, this leads to a host of issues that would interfere with his ability to live life normally and would likely remain at the veyr least up until Extremis. Especially since so much of how Tony values himself and how others value him is based on what his brain and hands can do. On the flip side, research into that could be deeply helpful to Rhody after his fall.

In conclusion, HIV+ Tony is a really interesting angst possibility.