Types of EDS

Ehlers-Danlos syndrome (EDS) is a group of inherited connective tissue disorders, caused by various defects in the synthesis of collagen. EDS is known to affect men and women of all racial and ethnic backgrounds.

There are six distinct types of EDS currently identified. All share joint laxity, soft skin, easy bruising, and some systemic manifestations. Each type is thought to involve a unique defect in connective tissue, although not all of the genes responsible for causing EDS have been found.

These six types are defined according to the signs and symptoms that are manifested, in a set of major and minor diagnostic criteria for each type. Each type of EDS is a distinct disorder that “runs true” in a family. This means that an individual with Vascular Type EDS will not normally have a child with Classical Type EDS. There a number of mutations identified as Ehlers-Danlos syndromes since the 1997 diagnostic criteria; these lie outside the classifications and can be located through the OMIM/Online Mendelian Inheritance in Man® database from Johns Hopkins University. The types are:

  • (Type III - Hypermobility Type)This is the most common type. To date, no distinctive biochemical collagen finding has been identified by researchers. Inherited in an autosomal dominant manner.

  • (Type I & II Classical) Marked by occasional internal organ fragility. In some families type V collagen is affected (abnormal electrophoretic mobility of proa1(V) or proa2(V) chains) as well as type I. Inherited in an autosomal dominant or recessive manner.

  • (Type IV Vascular) Marked by fragility of arteries, intestines & other internal organs. Caused by structural defects in the proa1(III) chain of collagen type III, encoded by the COL3A1 gene. Inherited in an autosomal dominant manner. VEDS incidence is estimated at one in 250,000; particularly serious because of possible arterial or organ rupture.

  • (Type VI-kyphoscoliosis type) Very rare; it is marked fragility of eyes and arteries. It is the result of a deficiency of lysyl hydroxylase (procollagen-lysine 5-dioxygenase, or PLOD), which is a collagen-modifying enzyme. Inherited in an autosomal recessive manner. Can be diagnosed through urine test.

  • (Type VII-A&B - Arthrochlasia Type) Very rare caused by mutations leading to deficient processing of the amino-terminal end of proa1(I) [type A] or proa2(I)[type B] chains of collagen type I. Inherited in an autosomal dominant manner. Can also be diagnosed by skin biopsy.

  • (Type VII-C - dermatosparaxis type) Very rare caused by a deficiency of procollagen I N-terminal peptidase. Inherited in an autosomal recessive manner. Can be diagnosed by skin biopsy.

The types may appear clear and defined, but EDS rarely permits easy classification. Although the type almost always runs true within each family, the symptoms of individual family members can vary so widely from each other that EDS is either misdiagnosed or ignored, and therefore is probably more frequent than previously thought. Current research estimates incidence at one in 2,500 to 5,000.