The Ehlers-Danlos syndrome: on beyond collagens

The Ehlers-Danlos syndrome (EDS) is a clinically and genetically heterogeneous connective tissue disorder affecting as many as 1 in 5,000 individuals (1). EDS is characterized in its most common form by hyperextensibility of the skin, hypermobility of joints often resulting in dislocations, and tissue fragility exemplified by easy bruising, atrophic scars following superficial injury, and premature rupture of membranes during pregnancy. The recognition of frequent ultrastructural abnormalities of collagen fibrils in EDS patients led to the concept that EDS is a disorder of fibrillar collagen metabolism (2). Following the identification of specific mutations in the genes encoding collagen types I, III, and V, as well as several collagen processing enzymes, the EDS classification scheme was collapsed into six distinct clinical syndromes (3), emphasizing the molecular basis of each form (Table ​(Table11). Table 1 The Villefranche classification of EDS Heterogeneity between the several clinical syndromes both complicates the diagnosis of EDS and makes accurate diagnosis imperative. Ultimately, one would like to be able to establish a molecular diagnosis for each EDS patient. This is a laudable goal because it may allow improved genetic counseling through correlation of mutant genotypes with specific outcomes or complications. However, as outlined below, the molecular defects described to date are not sufficient to explain disease in many EDS patients, including those with the most common classical and hypermobility types. As a result, the search for EDS genes recently has expanded beyond the collagens and collagen-modifying genes. An understanding of the complete complement of genes and proteins involved in EDS and the precise mechanisms by which they cause disease may teach us much about normal collagenous matrix deposition and remodeling. These processes are of critical importance during development, wound healing, and aging.