The supervillain Apocalypse infected baby Cable with an techno-organic virus – and it would have killed him had Cyclops and Madeyne not decided to send him to the future where a treatment would be available.
Without getting too bogged down in the details (Cable’s origin is one of the most complex in Marvel Comics), Cable a.k.a.
As a result, while the techno-organic virus isn’t killing Cable, but it has permanently turned him into a cyborg with a metal arm and cybernetic eye.
Nathan Summers was born as the son of the X-Men hero Cyclops and a clone of Jean Grey named Madelyne Pryor.