Understanding Hypermobile Ehlers-Danlos Syndrome

What Is Hypermobile Ehlers-Danlos Syndrome?

Hypermobile Ehlers-Danlos Syndrome (hEDS) is a genetic condition that affects connective tissue throughout the body. Connective tissue is the material that holds your body together—it's found in your skin, joints, blood vessels, and organs. In people with hEDS, this connective tissue doesn't work the way it should because of a genetic difference that affects how collagen is made or used.

The condition is inherited, meaning it passes down through families. If one parent has hEDS, there's roughly a 50% chance each child will inherit it. The genetic change typically involves a gene called COL3A1, though researchers continue to study other genes that may play a role. hEDS is classified as a rare disease, affecting an estimated 1 in 2,500 to 1 in 5,000 people worldwide, though some experts believe it may be underdiagnosed.

The name "hypermobile" refers to the increased flexibility of joints. People with hEDS often have joints that bend more than typical—sometimes called double-jointed. However, this flexibility comes with a cost: joints are less stable, ligaments and tendons are more fragile, and injuries happen more easily. This combination of extreme flexibility paired with weak connective tissue creates the core challenge of living with hEDS.

The condition exists on a spectrum. Some people experience mild symptoms and live relatively unaffected lives, while others face significant daily limitations. Symptoms can include joint pain, frequent dislocations or subluxations (partial dislocations), chronic fatigue, digestive problems, and cardiovascular issues. The severity may also change over time, sometimes improving with age or worsening during periods of stress or activity.

Practical Takeaway: Understanding that hEDS affects connective tissue throughout the entire body—not just joints—helps explain why symptoms can seem scattered across different body systems. Keeping track of which symptoms appear in your own experience will be useful when discussing hEDS with healthcare providers.

How hEDS Develops: Genetics and Connective Tissue

Collagen is a protein that acts like a scaffold holding your body together. It provides strength and structure to skin, tendons, ligaments, blood vessels, and organs. In people without hEDS, collagen is organized and cross-linked in a way that gives tissue both strength and flexibility. In hEDS, a genetic mutation affects how collagen is built or stabilized, resulting in collagen that is weaker or less organized.

For most cases of hEDS, the genetic change involves the COL3A1 gene. This gene contains instructions for making type III collagen, a form of collagen found throughout the body in blood vessel walls, skin, and connective tissues. When this gene has a mutation, the collagen produced may be malformed or unable to cross-link properly. The result is connective tissue that stretches too easily and provides less support than it should.

What makes hEDS different from other forms of Ehlers-Danlos Syndrome is that the classical and vascular forms involve different genetic mutations that produce different symptoms. Classical EDS primarily affects skin and joints but is generally less severe than vascular EDS. Vascular EDS, caused by mutations in COL3A1 as well, affects blood vessel walls and carries much higher risks of sudden vessel rupture—a life-threatening emergency. hEDS, while serious, does not typically involve the same vascular catastrophe risk as vascular EDS, though some people with hEDS may have cardiovascular complications.

Inheritance works in what geneticists call an autosomal dominant pattern. This means you need only one copy of the mutated gene to develop hEDS—you inherit it from one parent who also has the condition. When a parent with hEDS has children, each child has a 50% chance of inheriting the mutation. In rare cases, a person with hEDS may have inherited the mutation from a parent who had no symptoms or a very mild case, or the mutation may have occurred spontaneously during the formation of a parent's egg or sperm cell.

Practical Takeaway: Learning about your family history is important. If you have hEDS, discussing genetic testing and inheritance patterns with a genetic counselor can help you understand the condition better and make informed decisions about future children.

Common Symptoms and How They Develop

Joint hypermobility is the hallmark symptom of hEDS. Many people with the condition can bend their fingers backward, touch their thumb to their forearm, or perform other flexibility feats that seem impossible to most people. While this flexibility might seem like an advantage, it creates serious problems. Loose ligaments and weak connective tissue around joints mean they move beyond their intended range. This excess movement causes the cartilage inside joints to wear unevenly, leading to pain, swelling, and early-onset arthritis.

Dislocations and subluxations are frequent in hEDS. A dislocation occurs when a bone slips completely out of its socket; a subluxation is a partial slip. In severe cases, joints may dislocate during everyday activities—reaching for something on a shelf, rolling over in bed, or even from coughing or sneezing. Some people learn to self-reduce (pop the joint back in place) themselves, which can become a repeated cycle of injury and pain.

Chronic pain affects most people with hEDS, often in multiple locations. The pain stems from joint instability, muscle tension (as muscles work overtime to compensate for loose ligaments), and recurring micro-injuries. Pain may be constant or intermittent, and it often worsens with activity or weather changes. Some people describe their pain as deep, aching, and diffuse rather than sharp.

Gastrointestinal problems are common because hEDS affects the connective tissue in the digestive system as well. Many people experience reflux (acid backup into the esophagus), bloating, constipation, or diarrhea. In more severe cases, people develop gastroparesis (stomach muscles don't contract properly) or other motility disorders. Some research suggests that 30-90% of people with hEDS experience digestive symptoms.

Other symptoms include easy bruising (connective tissue in blood vessels is fragile), slow wound healing, skin that feels velvety or stretches easily, fatigue that may be severe and disproportionate to activity level, and anxiety or panic disorder (which occurs more frequently in hEDS than in the general population). Some people experience dysautonomia—a condition where the autonomic nervous system doesn't regulate blood pressure and heart rate properly—leading to dizziness, fainting, or heart palpitations.

Practical Takeaway: Create a symptom diary documenting what hurts, when it hurts, what activities made it worse, and what provided relief. This record becomes invaluable for healthcare providers and helps you identify patterns in your own condition.

Getting a Diagnosis: Tests and Specialists

Diagnosing hEDS can take years. Many people visit multiple doctors before receiving an accurate diagnosis because symptoms overlap with other conditions like fibromyalgia, chronic fatigue syndrome, and anxiety disorders. As of 2017, the Ehlers-Danlos Society published updated diagnostic criteria that made diagnosis more straightforward, but many healthcare providers are still unfamiliar with these criteria.

There is no single definitive blood test for hEDS in most cases. Diagnosis begins with a clinical evaluation. A specialist (typically a geneticist, rheumatologist, or specialized internist) reviews your personal history of symptoms and your family medical history. They perform a physical examination that includes testing for hypermobility using the Beighton score, which involves nine tests of flexibility. A person with hEDS typically scores 5 or higher on this 9-point scale. However, the Beighton score alone isn't enough for diagnosis—it must be combined with a history of symptoms and exclusion of other conditions.

Genetic testing is available for some forms of hEDS but not all. If a mutation in COL3A1 is found, it confirms the diagnosis. However, many people with hEDS have no identifiable genetic mutation—their test comes back negative despite clear clinical symptoms. This doesn't mean they don't have hEDS; it means the specific genetic cause hasn't been identified. Researchers continue to discover additional genes involved in hEDS, so negative genetic tests may change over