Why do some people have learning disabilities?

Specific Learning : Disorder is diagnosed in school-age children with avg. to > avg. IQ's. Some families have mutant genes for Specific Language Impairment & resultant Reading Disorder & Disorder of Written Expression. Math impairment may be from Non-Verbal Learning Disability, associated with many syndromes, some of which are inheritable. Low birthweight, brain infections, trauma & trauma are some other causes.