Since each brain must learn to read from scratch, as Wolf put it, “many things can happen along the way.” Dyslexia, originally called word-blindness, is a neurobiological condition describing the failure to read words and letters affecting an estimated 10-20 percent of schoolchildren, depending on whom you ask.

http://ww2.kqed.org/mindshift/2015/10/01/understanding-dyslexia-and-the-reading-brain-in-kids/?utm_source=facebook.com&utm_medium=social&utm_campaign=npr&utm_term=nprnews&utm_content=202503