Arthrochalasia Ehlers-Danlos Syndrome · aEDS

Description

Arthrochalasia Ehlers-Danlos Syndrome (aEDS) is an autosomal dominant connective tissue disorder caused by heterozygous variants in COL1A1 or COL1A2 that disrupt the N-terminal propeptide cleavage site of type I procollagen. Most reported variants alter or skip exon 6, removing or distorting the cleavage recognition sequence so that the N-propeptide is retained on a fraction of the pro-α chains. Partially processed chains are then incorporated into collagen fibrils, producing the structural defect that drives the phenotype. The biochemical step that fails in aEDS is the same step that fails in dermatosparaxis EDS, with the substrate defective in aEDS and the enzyme defective in dEDS.

The hallmark clinical finding is congenital bilateral hip dislocation, present at birth in nearly all reported cases. Additional features include severe generalized joint hypermobility with recurrent subluxations, soft skin with mild hyperextensibility, easy bruising, muscle hypotonia, kyphoscoliosis, and reduced bone density. Tissue fragility is less prominent than in classical or vascular EDS. Fewer than 50 affected individuals have been reported in the medical literature, which makes aEDS one of the rarest entries in the EDS taxonomy.

The 2017 international classification by Malfait and colleagues in the American Journal of Medical Genetics Part C lists three major criteria: congenital bilateral hip dislocation, severe generalized joint hypermobility with multiple dislocations and subluxations, and skin hyperextensibility. Minor criteria include muscle hypotonia, kyphoscoliosis, radiographically mild osteopenia, tissue fragility including atrophic scars, and easy bruising. Diagnosis requires the major criterion of congenital bilateral hip dislocation plus either of the other two major criteria, plus confirmatory testing. Confirmatory testing is sequencing of COL1A1 and COL1A2 with attention to exon 6 and the N-propeptide cleavage site, supported by biochemical analysis of dermal fibroblast culture for the partially processed pN-collagen species when needed.

Treatments to date

Management is supportive and orthopedic. There is no disease-modifying therapy and no clinical trial program targeting the molecular defect.

Hip dislocation present at birth is the central early management problem. Reduction is challenging given the underlying connective tissue laxity, and recurrent dislocation despite closed reduction or surgical stabilization is common in the published cohort. Orthopedic surgeons experienced with EDS phenotypes coordinate operative planning, and outcomes are better when soft tissue fragility is anticipated in preoperative consent and intraoperative technique. Physical therapy supports muscle control around hypermobile joints through childhood and adulthood without forcing extreme range.

Spinal monitoring tracks kyphoscoliosis, with bracing or surgical correction considered on the curves and timelines used in other connective tissue disorders. Bone density screening is appropriate given reduced bone mineralization in the published cohort, with calcium and vitamin D repletion as first-line measures and bisphosphonate consideration where fracture risk supports it. Skin care follows general EDS principles, with attention to wound closure technique and adhesive selection.

Pregnancy management uses maternal-fetal medicine input given joint instability of the pelvis, the possibility of premature rupture of membranes reported in some cases, and connective tissue considerations during delivery. Genetic counseling addresses the 50 percent transmission risk and the rarity of the diagnosis, which means family planning conversations often draw on a small published evidence base.

No registry-scale natural history study has been completed for aEDS, and most published outcome data remain at the case-series level.