Ehlers-Danlos Syndrome (EDS) is a heterogenous connective tissue condition characterized by joint hypermobility and skin hyperextensibility. Though initially characterized as “genetic” by newly-minted medical geneticists in the 1950s, medical geneticists in the 2020s are increasingly turning away EDS patients, arguing that they are not responsible for them, and questioning if EDS is genetic, or even real at all. In this project, I trace patient and physician experiences with EDS from the early 20th century through the recent past, aiming to understand how it has become such a controversial disease category. I position EDS as a “contested illness,” considering how genetics mediates disease legitimacy and identity. Ultimately, I argue that EDS represents an important lens on relationships between genetics and chronic illness, and more broadly between technology, disease diagnosis, and identity. What makes a disease “genetic”? And what are the stakes, for institutional organization, physician professionalism, patient care and identity?