I've seen some research (poster presentations, mostly, but I might find published journal articles, too, if I looked for them) on systematic underidentification of giftedness among students with LDs, including dyslexia. The field is still struggling with designing and implementing best practices in this area. There are many unanswered questions; you could probably build a dissertation, or two, or fifty out of answering them.
I probably find a previously-unidentified GT/dyslexic every other year or so, among my secondary students. This doesn't even include the ones who are still skating by, and don't rise to my attention.
