Finally, mutations in the COL5A1 and COL5A2 genes that encode the chains of type V collagen cause Ehlers-Danlos syndrome types I and II [22], [23], which are characterized, among other defects, by skin laxity, a feature of the Crtap-/- mice. This evidence concerns the gene CRTAP and Ehlers-Danlos syndrome, classic type, 1.