Probably a week does not go by where I haven’t heard something like the following from a bleary eyed parent: “The school is telling us that no one really knows what dyslexia is and if anyone really does it has to be a medically diagnosed.” 

We have talked about this before in different ways, but I thought that “deconstructing dyslexia” would be helpful. 
The definition that follows from NICHD is very useful:
Dyslexia is a specific learning disability that is neurological in origin.
OK…so far so good. This tells that the disorder is likely to have been passed down. 99% of the time in my work I find one or the other parent saying something, like “Yep, I was just like that as a kid.”
It is characterized by difficulties with accurate and / or fluent word recognition and by poor spelling and decoding abilities.  
What??? Where is all of the [b/d],  [was/saw] reversal business everybody always talks about? You mean that has nothing to do with it? Accurate and or fluent word recognition? I don’t know too many medical doctors testing that stuff.  
These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction.
You mean they aren’t even mentioning IQ? Why do the schools still hold to the sanctity of the IQ score?
 Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge
Well, if you read  a word like “prickopinny” for “porcupine” it certainly will affect comprehension, won’t it?   Also, if you don’t read much, as dyslexic people usually don’t, then vocabulary and comprehension will suffer.
Now, doesn’t that make sense?