A family with Ehlers-Danlos syndrome type III/articular hypermobility syndrome has a glycine 637 to serine substitution in type III collagen.

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of heritable disorders of connective tissue. The type III variety is characterized by joint hypermobility and minor hyperextensibility and softness of the skin. While collagen fibril structure has been shown to be abnormal in such patients, the underlying molecular defect(s) has not been determined. Here we characterize the first mutation found in a family with EDS III. Analysis of cultured fibroblasts from the affected family revealed intracellular retention of type III collagen. This is usually a biochemical characteristic of EDS IV, caused by mutations of COL3A1. Analysis of the cDNA sequence in this EDS III family revealed a glycine to serine mutation at amino acid residue 637 of the type III collagen molecule. This was confirmed by allele-specific oligonucleotide hybridization against amplified genomic DNA. Thus mutations of type III collagen can cause either EDS IV or EDS III. Two affected family members had virtually normal skin and so more closely resembled the phenotype of articular hypermobility syndrome.