Harvard is one of the most selective institutions in the universe, as “The Dean" suspects you already know. Many outstanding applicants are turned away each year. If you have a learning disability but can submit an application that demonstrates that you belong at Harvard, you will be in the running. For instance, if you are a brilliant writer and yet you struggle with math, then you will be evaluated based on what you HAVE achieved and not on what you haven't. Similarly, if your standardized test scores are below the Harvard norms, but you have been successful both in and out of the classroom, admission officials may cut you some slack on your tests if you provide documentation of your learning disability. However, the admission folks don't want to set up any candidate for failure, so your application will have to prove that you can handle a rigorous curriculum in a competitive environment.
If your learning disability has limited you in some ways but you have excelled in others, then you should feel free to give Harvard a shot. But, again, Harvard sets the bar very high for ALL applicants, so if you have deficiencies in one or more areas due to your learning disability, you will have to show Harvard that you are exceptional in others.
Finally, before you apply to Harvard (or anywhere else), do your “homework." If you will require accommodations for your learning disability after you enroll in college, you should research the services available on campus as well as the documentation required to get these services For more information from Harvard's Accessible Education Office, see http://aeo.fas.harvard.edu/documentation.html The mere fact that Harvard actually has an “Accessible Education Office" suggests that you won't be alone if admitted. But “The Dean" did have to dig pretty deep to find it!