Hey, I have dysgraphia and dysautonomia. There's one article I saw on this topic that says that the underlying cause for the dysautonomia, or the dysautonomia itself can cause issues with things like lexiconization, one of the major issues in dyslexia. However it's a theory as we lack the machinery to clearly see the issue and (my own thoughts) as dyslexia happens early on in development, one would need to look early on at the developing brain. I know a couple of people with both dysautonomia conditions and a learning disorder so it seems quite possible.
Regular google isn't very good for these type of questions. I suggest google scholar and Pubmed.
http://scholar.google.com/
http://www.ncbi.nlm.nih.gov/pubmed/
When I try on google scholar, I found that JHS (joint hypermobility syndrome) offers a possible "missing link" between dysautonomia and dyslexia. See this article: http://rheumatology.oxfordjournals.org/cgi/content/full/44/6/744 This article actually seems to touch on several of the problems you described in your lengthier previous post, so I think it might definitely be something to look into. If you want to know more about the link between dysauto and JHS/EDS, post a question about that on the board and someone should be able to help you find our old threads on the subject; we've had quite a few. (That's the one article I found in a quick search myself; I would encourage you to go ahead and pursue it further using google scholar rather than regular google since I didn't have time to do an exhaustive search myself.)
Nothing comes up on pubmed with both search terms dysautonomia and dyslexia.
POTS has been linked to attention difficulties specifically, but patients frequently report a wide range of cognitive issues and studies regarding cerebral perfusion have yielded conflicting results. Other than the study I pointed you to from my google scholar search, I haven't seen anything specific re: dyslexia.
Don't know about dyslexia specifically. Definitely measurable cognitive dysfunction. I have problems with memory and language.