Myth
“HSD is just mild EDS.”
Fact
Pain, fatigue and dislocations can be every bit as severe in HSD as in hEDS. Both deserve the same seriousness and care plan.
Mechanisms involved
This condition is explained through the mechanisms below. Each one is taught as ordinary physiology first.
Primary
Secondary / contributing
Immune cells involvedWho is actually in the tissue
Connective tissue is the immune system's terrain, so changing the terrain changes the response.
Selected cell
Mast cell
Tissue sentinel packed with histamine, tryptase and prostaglandin granules. When it degranulates it recruits and sensitizes nearby nerve endings.
Mast cells live in connective tissue matrix. Altered matrix appears to change how readily they activate, which is one theory behind the hEDS–MCAS overlap.
Schematic drawings, not micrographs. Immune findings here describe mechanism and association; none of them are diagnostic tests.
What it is
Ehlers-Danlos syndromes are inherited connective-tissue disorders — the collagen that should hold joints, skin and blood vessels firmly is built a little too loosely. The 2017 classification recognizes 13 types; all but one have an identified genetic cause. The hypermobile type (hEDS) is by far the most common and is still diagnosed clinically, since no single gene for it has been found. A related diagnosis, Hypermobility Spectrum Disorder (HSD), sits nearby on the same clinical spectrum: the management principles and potential seriousness are the same, even though the diagnostic checklist differs.
How the mechanisms produce this
- Loose connective tissue affects joints, skin and vessel walls throughout the body, so hypermobility rarely travels alone.
- Compliant vessel walls can contribute to blood pooling on standing, connecting the tissue mechanism with dysautonomia and POTS.
- Mast cells live within connective tissue. hEDS, dysautonomia/POTS and MCAS are commonly seen together — often called the ‘trifecta’ — although that overlap does not yet prove one shared cause.
- The underlying genetics do not change, but infections, environmental exposures, surgery and hormonal shifts can change how loudly the phenotype is expressed.
HSD vs hEDS
Myths and facts
Myth
“You need a positive gene test for ‘real’ EDS.”
Fact
hEDS has no identified gene yet. A normal panel may help rule out other EDS types, but it does not rule out clinically diagnosed hEDS.
Myth
“If your Beighton score dropped, you do not have it anymore.”
Fact
Hypermobility often decreases with age. Clinical assessment can account for historical hypermobility, so the condition does not disappear when someone becomes stiffer.
What tends to help
- Physical therapy focused on joint stabilization, motor control and gentle strengthening, while avoiding overstretching.
- Bracing, orthoses, compression and taping can provide useful sensory feedback; small studies report measurable improvements in postural stability and shoulder proprioception.
- Pacing and treating co-travellers such as POTS and MCAS can reduce the total symptom load, including strain around unstable joints.
- Periodic cardiovascular check-ins are reasonable because connective-tissue changes can involve blood vessels, with the schedule individualized by a clinician.
Where the evidence is thin
No single gene has been identified for hEDS, so diagnosis still rests on clinical criteria rather than a definitive test.
References
- 01Malfait et al. — 2017 International Classification of the Ehlers-Danlos Syndromes
- 02Dupuy et al. — Somatosensory orthoses and postural control in hEDS (pilot study)
- 03Tudini et al. — Kinesiology taping and shoulder proprioception in hEDS (randomized trial)
- 04The Ehlers-Danlos Society — hEDS and HSD comparison