Ehlers-Danlos syndrome (EDS) is a rare condition that appears in at least 1 in 5,000 people worldwide, according to the National Institutes of Health (NIH) Genetics Home Reference. More people became aware of the syndrome in October 2019 when famous singer-songwriter Sia revealed in a series of tweets that she has EDS. Others with EDS responded in droves online, often referring to those in their community as “zebras.”
According to the international Ehlers-Danlos Society, the reference to zebras is borrowed from a common expression heard in medicine: “When you hear hoofbeats behind you, don’t expect to see a zebra.” In other words, medical professionals are typically taught to look out for more-common ailments rather than testing for ultrarare diagnoses. Due to this approach, people with EDS and related disorders can sometimes be left in the lurch, hunting for explanations about their health that few doctors can readily provide.
The EDS community adopted the zebra as its mascot because “sometimes when you hear hoofbeats, it really is a zebra.” In this spirit, The Ehlers-Danlos Society includes patients, caregivers, health care professionals and supporters working “towards a time when a medical professional immediately recognizes someone with an Ehlers-Danlos syndrome.”
EDS disrupts the integrity of connective tissues in the body that normally support the skin, bones and blood vessels, as well as many muscles, according to the NIH. The condition may range from mildly bothersome to potentially life-threatening. Although the syndrome manifests differently in different people, many patients with EDS display a large range of joint movement, known as hypermobility; poor muscle tone; and loose, velvety skin prone to bruising and scarring.
These symptoms are not universal. As of 2017, a diagnostic manual titled “The International Classification for the Ehlers-Danlos Syndromes” characterized 13 distinct forms of EDS, each with its own array of defining features and underlying causes, according to the National Organization for Rare Disorders (NORD). Many of these forms share characteristics, such as unstable joints or fragile heart valves and blood vessels, but specific traits may be unique to particular subtypes, according to the Hypermobility Syndromes Association.
Despite their wide variation, most forms of EDS appear to stem from related genetic mutations, according to NORD. Some of the affected genes contain instructions for building collagen, a fibrous protein that strengthens connective tissues throughout the body and comes in a variety of subtypes. Other genes help determine how the body processes collagen and how other structures interact with the protein, and these genes may also have functions beyond those related to connective tissue, according to the NIH.