The Ehlers-Danlos syndromes are a heterogeneous group of syndromes that cause laxity and weakness of ligaments, skin, and blood vessels.
There are at least nine clinical and genetic subtypes, all of which are caused by mutations in fibrillar collagen genes and genes that modify fibrillar collagen. For ex- ample, Ehlers-Danlos type I is an autosomal dominant disorder caused by a mutation in the gene that is coding for collagen type V, which is important for forming collagen I fibrils. This defect in fibril formation leads to decreased ligament stiffness and joint laxity. Marfan’s syndrome is an autosomal dominant disease caused by a defect in the gene that is coding for fibrillin. Fibrillin is a large glycoprotein that is a structural component of elastin-containing microfibrils. The gene defect results in decreased fibrillin forma- tion and a structurally weakened elastin. As elastin is one of the structural proteins in ligaments, clinical manifestations of the dis- ease include ligament laxity, loose joints, and other connective tissue problems, such as aortic dilation.