Barbara Bliss had the following insight into this question:
“The term ‘learning disability’ tends to infer that a person cannot learn. With the proper instruction, dyslexics do learn. The degree of difficulty a dyslexic person has with reading, spelling, and/or speaking varies due to the type of teaching the person receives as well as the differences in the brain organization. The brain is normal, often very ‘intelligent’, but with strengths in areas other than the language area. Such brain differences appear to be inherited, probably from more than one ancestor. They are hidden, usually, until the person goes to school and attempts to learn by reading and communicate by writing.”