Apparently there's been an incorrect rumour that
Deus Ex: HR would feature dynamic dfficulty.
Not the case, says Producer David Anfossi, quoted at PC Gamer:
“I don’t know who said that,” said Anfossi of Birch’s comments, “but that person was either drunk or doesn’t work here.” He made it very clear: “No. We have three difficulty settings: Easy, Normal and Hard. There’s no adaptation of the difficulty at all, we don’t have anything like that.”
More information.