What are hypermobile Ehlers-Danlos syndrome and hypermobility spectrum disorder?
Hypermobile Ehlers-Danlos Syndrome (hEDS)
The Ehlers-Danlos syndromes (EDS) are a group of 13 connective tissue disorder types that vary both in how they affect the body and in their genetic causes (click here to see all 13 types).
The hypermobile type of Ehlers-Danlos syndrome is thought to arise from alterations in the body's dominant structural protein, collagen. Collagen occurs throughout the body, including the skin, fascia, gut, lungs, joints, blood vessels, bladder, bowel and pelvic organs. It forms molecular cables that strengthen the tendons, the skin and internal organs. It should provide structure to our bodies, protecting and supporting the softer tissues and connecting them with the skeleton. It is thought however, that in those with EDS, the collagen fibres, which cover the body (externally and internally), are faulty; collagen density is reduced and elastic fibres are fragmented.
Although generally inherited from a parent with the same single or multiple gene mutation(s), it is also possible for a child to be born with EDS as a result of a ‘de novo gene mutation’ (Levy H.P. 2004). This means that an alteration in a gene(s) is present for the first time in one family member (there may be no previously affected family members). The proportion of EDS cases caused by De Novo mutations is unknown. Unlike the rarer types such as classical or vascular EDS, the hypermobile type of Ehlers-Danlos syndrome (hEDS) is now thought to be common, and the prevalence of hypermobility spectrum disorder (see below) is higher still.
‘hEDS is now considered the commonest EDS variant, with an unexpectedly high disability potential.'
(Castori M. 2012 - Medical Genetics Dept. of Molecular Medicine)
As yet, there is no genetic test for hEDS, so clinical diagnosis (to look for musculoskeletal and faulty connective tissue signs and symptoms, as well as any a family history of the condition) is required. hEDS is generally characterised by hypermobility and often instability (subluxation/dislocation) at the joints, with joint pain and soft tissue injury; abnormal skin (mild papyraceous scars, slow wound healing and easier than ‘normal’ bruising); and other weaker body tissues, e.g. weak abdominal wall leading to hernias; pelvic floor prolapse; stretchy blood vessels; and varicose veins. Associated disorders (also known as comorbidities) such as cardiovascular autonomic dysfunction (tachycardia and/or low blood pressure); gastrointestinal dysfunction (reflux, sluggish bowel, intolerances); and anxiety disorders may also be associated. Importantly, hEDS is not associated with weakness or rupture of major blood vessels or bowel wall.
How do the effects of defective collagen manifest themselves as symptoms in hEDS?
The most commonly recognised symptom is hypermobility of the joints. In hEDS a person’s joints are lax because they have inherited looser and stretchier connective tissues. In addition, the bony sockets in knees, hips and shoulders are often found to be more shallow in those with this condition. Hypermobile people can easily injure soft tissues around joints because their joints can twist or over-extend easily. This reduced stability in the joints can lead to symptoms such as pulled tendons and ligament sprains, tendon tears, joint pain, clicking joints, loose/unstable joints that subluxate and/or dislocate easily, disc prolapse. In addition to joint hypermobility related symptoms, many other symptoms are also commonly seen in those with hEDS, arising either as direct complications of hEDS or as associated disorders. These include: acute pain. persistent, often widespread pain, neuropathic pain, extreme tiredness (persistent fatigue), proprioceptive dysfunction, skin that may bruise, stretch or scar more easily, pelvic floor weakness, bladder over-activity, functional gastrointestinal disorders, cardiovascular autonomic dysfunction (inc., feeling faint and/or heart palpitations, resistance to local anaesthetic, anxiety, earlier than ‘normal’ onset of osteoarthritis, allergies/mast cell activation. The associated disorders affect people in different ways, but in many cases are even more debilitating than the more commonly recognised musculoskeletal symptoms; they seriously affect quality of life and need to be properly managed as part of holistic treatment.
(Ref: HMSA 2014 & 2017 / Tinkle B. et al 2017 / Castori M. et al 2017 / Henderson Sr. F.C. et al 2017)
Hypermobility Spectrum Disorder (HSD)
When symptomatic joint hypermobility is experienced, but individuals do not fully meet for hEDS (or any other heritable disorder of connective tissue) a patient may be given a diagnosis of ‘hypermobility spectrum disorder (HSD).
HSD is a group of four different categories (see below), created to better identify subtypes of symptomatic hypermobility.
As shown in the box above, the four different HSDs which may be identified are:
• Generalised (joint) hypermobility spectrum disorder (G-HSD): G-HSD is diagnosed where generalised joint hypermobility has been assessed using the Beighton score and a patient is also affected by one or more secondary musculoskeletal manifestation such as:
• Musculoskeletal / soft tissue trauma
• Degenerative joint and bone disease
• Disturbed proprioception
• Other musculoskeletal / orthopaedic traits
• Peripheral (joint) hypermobility spectrum disorder (P-HSD): P-HSD is diagnosed where joint hypermobility is limited to hands and feet, plus one or more secondary musculoskeletal manifestation (see bullet point list above).
• Localised (joint) hypermobility spectrum disorder (L- HSD): L-HSD is diagnosed where joint hypermobility is found at single joints or group of joints, plus one or more secondary musculoskeletal manifestation regionally related to the hypermobile joint(s) (see bullet point list above).
• Historical (joint) hypermobility Spectrum Disorder (H-HSD): H-HSD is diagnosed when symptoms of symptomatic generalised joint hypermobility are reported historically/self-reported by the patient; the joint(s) having, perhaps, stiffened with age or having been affected by surgery or disability. The Beighton score is negative, and the patient is affected by one or more secondary musculoskeletal manifestation
HSD, just like hEDS, can have significant effects on health, and actually form part of a diagnostic continuum (see image A) . In fact, from a clinical perspective, asymptomatic joint hypermobility, HSDs, and hEDS can all be brought back to a single continuous spectrum ranging from isolated joint hypermobility at one end to hEDS at the other (passing through the various HSDs along the way):
Is hEDS worse than HSD?
Not necessarily. ‘Both sit on a vast spectrum and can cause the same symptoms. The spectrum acknowledges that there can be severe effects on lives, whether they’re the direct result of joint hypermobility, or because they are known to be associated with having joint hypermobility. What is important is that the problems that arise, whatever the diagnosis, are managed appropriately and that each person is treated as an individual. Both disorders can be equal in severity but, more importantly, both need similar management, validation and care’ (1 & 2 Ehlers-Danlos Society 2017).
To fully understand the whole range of variations seen in the spectrum spanning joint hypermobility, through hypermobility spectrum disorders and hEDS, it is likely that geneticists will need to look towards a genetic model that allows for the expression of the single or multiple gene mutation(s) to be further influenced by other genetic, environmental, or constitutional factors.
For many people, the distinction between hypermobility spectrum disorder and the hypermobile type of Ehlers-Danlos syndrome not an important one 'clinically', as treatments are similar. 'Exceptions include more severely affected patients, such as those who require braces or surgery to stabilise their joints and who also experience other complex problems, such as weakness or loss of feeling in arms or legs, and those with certain eye problems or a family history of aneurysms, all of whom if possible should see a specialist with knowledge of EDS, in part to rule out other more serious types of EDS.' (Dr Alan G. Pocinki MD PLLC).
It is thought that hypermobility spectrum disorder can arise from various aetiologies (originating causes). In many cases, these may have a genetic influence, being inherited as a genetic trait(s) in the same way as an individual inherits the traits for eye colour, body type or height. However, HSD can also be ‘acquired.
Inherited genetic traits
Research has not, as yet, progressed sufficiently to establish the molecular basis on which this inherited hypermobility takes place. HSD running through a family, may suggest it has a heritable / genetic basis, but then again it may not (3/Ehlers-Danlos Society 2017). In some families, cases may occur in scattered or isolated instances, segregate within families as single gene traits, or they may cluster in families as traits controlled by multiple genetic and/or environmental factors and constitutional factors (Castori M. et al 2017). More information on the multiple factors that can influence hypermobility can also be found on page 33 ‘Why are people so differently affected?'
Acquired symptomatic hypermobility Symptomatic hypermobility can be ‘acquired’ in various ways. For example some individuals acquire symptomatic hypermobility through:
• Injury - for example, dancers, gymnasts and sports people put themselves through gruelling workouts in order to produce graceful, flowing movements and may over-stretch joints, muscles and ligaments when trying to create the lines that are desirable.
• Overuse - e.g. massage therapists may acquire problems in their finger and thumb joints triggered by applying repetitive pressure through their joints.
• Malalignment - e.g. those with asymmetrical hip rotation, flat feet or unequal leg length may find that otherwise asymptomatic hypermobile joints become symptomatic over time.
• Physical weakening of tissues due to surgery resulting in symptomatic joint laxity.
• Musculoskeletal malalignment or malformation
• Pharmacological (medicine/drug) interference with collagen biosynthesis can increase joint laxity. (Refs: Beighton P.,
(Refs: Beighton P., Grahame R and Bird H. ‘89 & ‘99 / Oliver J.’05)
Certain medical conditions can also cause an individual to acquire symptomatic hypermobility, these include lupus and rheumatoid arthritis, which are autoimmune diseases. In these conditions, otherwise healthy connective tissue is attacked by the body’s own immune system, causing it to be defective (Punzi L. et al 2000).
‘Whenever symptoms commence, and irrespective of the cause of the hypermobility, the term “hypermobility syndrome” [now know as hypermobility spectrum disorder] is used to describe the condition. Even hypermobility in a single joint can cause pain and/or instability in that joint; the diagnosis may still be a hypermobility syndrome [hypermobility spectrum disorder] if there are other symptoms and signs.'
(Grahame R. 2012a)
Please note - More from the author of this website is available in the book Understanding Hypermobile Ehlers-Danlos Syndrome and Hypermobility Spectrum Disorder - available from Redcliff-House Publications
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