I can't really tell from just this picture. Are the scales there? Is it just a different coloration? Does it feel different to the touch? Does it bother her to be touched there?
My Dum has is all cream underneath but has a spot the same size in the same place of pure white scales (I don't know if it was from birth or a injury from before I got her).
Edit: I just looked at her again and its in the exact same spot- she's not cooperating for a picture. I'll try again latter.