More than 50% of cases of classical Ehlers-Danlos syndrome (EDS) are caused by mutations in the COL5A1 gene. Many of these mutations lead to a non-functional/absent pro-alpha1 (V) chain. As a result, type V collagen fibrils in the skin and other tissues cannot be assembled correctly. The fibrils are disorganized and larger than usual.
Research is going on how these changes in collagen structure cause the signs and symptoms of classical Ehlers-Danlos syndrome (EDS).