EDS Introduction and Types of EDS
Ehlers-Danlos syndrome (EDS) is the term used for a group of genetic connective tissue disorders that are characterized by skin hyperextensibility, joint hypermobility, and tissue fragility. The underlying pathophysiology in EDS involves inherited alterations in genes affecting the synthesis and processing of collagen.1 Patients suspected of having EDS based on their clinical presentation and family history should be referred to an expert in clinical genetics for confirmation of the diagnosis.
Six distinct EDS types are recognized using the Villefranche classification scheme, defined according to clinical features, as well as specific underlying genetic and biochemical defects.2 This revised nomenclature replaced the prior method of identifying the different forms by number. Under this classification, the 6 major types of EDS are identified as: classic, hypermobility, vascular, kyphoscoliosis, arthrochalasia, and dermatosparaxis. The 2 most frequently diagnosed forms of the condition are the classic and hypermobile types.
Joint hypermobility is the hallmark of most types of EDS. This can involve both proximal and distal joints. Assessment of the joints is accomplished using the Beighton hypermobility scale, which assigns points for the ability to perform each of 4 maneuvers, including dorsiflexion of the fifth finger >90 degrees, hyperextension of the elbow >10 degrees, hyperextensibility of the knee >180 degrees, and flexion of the waist with palms on the floor.2
Some forms of EDS are inherited in an autosomal-dominant pattern, including the classic, hypermobile, and vascular types of EDS. Heterozygocity for tenascin X deficiency can be associated with mild features of disease, including joint hypermobility.3
The hypermobile type of EDS is considered the least severe. Skin can appear velvety and hyperextensible. Striae distensae and piezogenic papules are present in classic and hypermobile types of EDS.