COL1A1 and Ehlers-Danlos syndrome, arthrochalasia type: An important differential diagnosis of dEDS is arthrochalasia EDS (aEDS), caused by heterozygous COL1A1 or COL1A2 defects leading to (partial) skipping of exon 6, which contains the ADAMTS2 cleavage site, causing retention of the N-propeptide of the affected collagen chain in mature collagen fibrils.62, 63, 64 Intriguingly, the phenotype of aEDS is quite different from that of dEDS.53