Now to further discuss on this.
Did you see the ruling of After the Battle with Revitalize?
If you payed a revitalize card for AtB, AtB checks to see if you discarded the card. But since, revitalize is a replacement effect, AtB will not allow you to draw 3.
If you apply this to Itachi.
If Itachi discarded himself, he was not discarded. He was Removed from game by his own mechanic, which is inherent.
Since he checks to see if the ninja was discarded, you would draw 2.
However, since inherent removed itachi from play, which is a mandatory replacement effect.
You would not draw 2 correct?