The Ehlers-Danlos Syndromes, abbreviated EDS, are a collection of often disabling inherited collagen defects which lend to weakened connective tissues throughout the entire body. Some involve insufficient collagen formation, others malformation of the collagen molecules, and /or of elements of the extra-cellular matrix in which collagen is formed up, lending to weaker tissues. Most are caused by known single point mutations or genetic defects also called "SNPs".
(Initial author's note: this seems like a good spot to include a note about the prevalence in the autistic population here, or maybe one paragraph down.)
This leads to all manner of body-wide issues, including - but not limited to - things like fragile or stretchy skin, frequent subluxations, frank dislocations, clumsiness, easy bruising, aneurysms, hernias, prolapses, CCI, CCA, tethered cord, incontinence, keloid scars, atrophic scars, myopia (nearsightedness), tendinitis, weak cartilage (early onset Osteoarthritis is common), chronic pain with no obvious/easy explanation in the absence of co-occurring auto-immune diseases, fibromyalgia and much more. (Source?)
As of September 21, 2022 there are currently 14 formally recognized types, of which 13 were described in the 2017 nosology put out by The Ehlers-Danlos Society (TEDS). The 14th type was recognized later in 2018, so is not yet in the formal nosology.
All but the most common type, hypermobile EDS, abbreviated "hEDS" have known genetic markers that can be tested for when suspected. Hypermobile EDS remains a clinical diagnosis to date.
Additionally, a new diagnostic category called the Hypermobility Spectrum Disorders or "HSD" was invented by TEDS under the 2017 nosology. This category has been intended to be a catch all for the many patients who show several signs of a form of connective tissue disorder, but none clearly matching any of the other similar Heritable Disorders of Connective Tissue (HDCTs) like Marfan Syndrome or Osteogenesis Imperfecta or Loeys-Dietz Syndrome, nor any of the rare forms of EDS.
But further, they do not tick off enough boxes on the arbitrary set of criteria for hEDS published in 2017.
Scientists are working hard around the world as of 2022 to try to uncover the gene(s) and or epigenetics that may lie behind the apparent familial hypermobile type of EDS (hEDS). The Norris Lab at the Medical University of South Carolina (MUSC) have fingered a gene based on one large family's presentation they have studied. Other studies are underway, but none have proven fruitful yet. It is also unclear if hEDS is purely genetic, and or possibly poly-genic. Many more SNPs and causes may well be uncovered as science progresses. (Sources to come.)