The rare disease status of Ehlers-Danlos syndrome (EDS) and hypermobility spectrum disorder (HSD) should be re-evaluated, as both conditions seem to be more prevalent than previously thought, a U.K. study suggests.

The study, “ Diagnosed prevalence of Ehlers-Danlos syndrome and hypermobility spectrum disorder in Wales, UK: a national electronic cohort study and case-control comparison ,” was published in the journal BMJ Open.

A nationwide Danish cohort study has reported that EDS, a connective tissue disorder, affects 20 per 100,000 people, an incidence that falls within the scope of a rare disease according to European Union standards (less than 50 cases in 100,000 people).

However, scientists are now convinced that the prevalence of EDS and HSD could be much higher than previously thought, because many patients are initially misdiagnosed, which can skew the estimations of disease prevalence. This underestimation could be problematic, as it may make physicians less likely to consider any of these conditions when examining and diagnosing patients.

“Establishing the diagnosis of EDS/HSD is often problematic for patients, which interferes with the early detection, treatment, and prevention of further escalations of recognized symptoms, disability and more elaborate complications,” the researchers wrote.

“It is possible that some of these difficulties arise from the widespread belief among clinicians that EDS is rare. It is therefore of clinical importance to establish better estimates of current prevalence,” they added.

In the study, researchers from Swansea University in the U.K. set out to evaluate the prevalence of EDS and HSD in Wales, in order to assess if these disorders could really fall under the category of rare diseases.

To that end, they carried out a case-control nationwide study based on the electronic medical records of patients who were diagnosed with EDS or joint hypermobility syndrome (JHS) between July 1990 and June 2017. The study included data gathered from primary care and hospital admissions in Wales. Of note, JHS has been classified as EDS or HSD since March 2017, according to the latest classification criteria.

Data obtained showed that within a period of 17 years, 6,021 people in Wales (70% women) had been diagnosed with EDS (957 people) or JHS (5,064 people). This corresponded to a combined EDS/JHS incidence of 10 cases per 5,000 people (194.2 per 100,000), which is above what would be considered a rare disease following EU standards.

The team also discovered a large discrepancy in the mean age of diagnosis between genders, with men being diagnosed approximately 8.5 years earlier than women.

In addition, they found that those with EDS/JHS were likely to receive therapeutic prescriptions for other disorders (e.g. musculoskeletal, gastrointestinal, and heart diseases), and also to be diagnosed with different types of illnesses, including mental, nervous, and digestive system disorders, within a period of one year before and after being diagnosed with EDS/JHS.

“We conclude that EDS/HSD are not rare conditions, and are associated with significantly increased odds of additional diagnoses and use of medications across many body systems. There is a large gender difference in the age of diagnosis, with many women not diagnosed until adulthood,” the researchers wrote.

“EDS and JHS have historically been considered rare diseases only affecting the musculoskeletal system and soft tissues. These data demonstrate that both these assertions should be reconsidered,” they added.