This post is something I learned about from the lovely Kristina, who runs the Defy Gravity blog. If you have POTS or another form of orthostatic intolerance and EDS, please check this out from the University of Washington:
Hypermobile EDS with postural orthostatic hypotension - search for identification of large kindreds.
Few disorders are more challenging than hypermobile Ehlers-Danlos Syndrome (formerly known as EDS type III) when trying to identify cause. Defining a population of patients with a clear clinical phenotype is an essential first step. We are actively recruiting individuals with hypermobile EDS and postural orthostatic hypotension (changes with blood pressure on standing or known abnormalities in autonomic testing) to recruit families with multiple affected family members with hypermobile EDS with or without autonomic alteration. The nature of the families and the number of individuals available will determine how each study is done. We will need detailed clinical information, may ask affected individuals to be seen in the Genetic Medicine Clinic at the University of Washington, and collect a blood sample to complete the study."