Ehlers Danlos Syndrome is caused by a defect in one of the
genes involved in collagen production. Some types of Ehlers Danlos Syndrome are known
to be related to a genetic flaw because of the observed inherited
pattern, but the exact defect may not be identified.
Classification of Ehlers Danlos Syndrome types was revised in 1997. The new
classification is simpler and based more on descriptions of the
actual symptoms. Ehlers Danlos Syndrome is now classified into six major types:
classical, hypermobility, vascular, kyphoscoliosis, arthrochalasia,
and dermatosparaxis, and a collection of rare or poorly defined
varieties.
Classical type
Under the old classification system, Ehlers Danlos Syndrome classical type was divided
into two separate types: type I and type II. The major symptoms
involve the skin and joints. The skin has a smooth, velvety texture
and bruises easily. Individuals with classical type Ehlers Danlos Syndrome typically
have extensive scarring at pressure points such as the knees, elbows,
forehead, and chin. Owing to loose joints, individuals are at
substantial risk for slowed motor development, poor muscle tone,
sprains, and partial or complete joint dislocations. Children may
have a tendency to develop hernias or other organ shifts within the
abdomen. Ehlers Danlos Syndrome classical type is inherited in an autosomal dominant
manner.
Hypermobility type
Excessively loose joints are the hallmark of this Ehlers Danlos Syndrome type, formerly
known as Ehlers Danlos Syndrome type III. Both large joints, such as the elbows and
knees, and small joints, such as toes and fingers, are affected.
Partial and total joint dislocations are common, and particularly
involve the jaw, knee, and shoulder. Many individuals experience
chronic limb and joint pain, although x rays are normal. The skin
may also bruise easily. Ehlers Danlos Syndrome hypermobility type is inherited in an
autosomal dominant manner.
Vascular type
Formerly called Ehlers Danlos Syndrome type IV, Ehlers Danlos Syndrome vascular type carries the risk of
premature death. The connective tissue in the intestines, arteries,
and uterus is unusually weak, leading to a strong possibility of
organ or blood vessel rupture. Such ruptures are more likely between
ages 20–40, although they can occur any time, and can be
life-threatening. The large joints have normal stability, but small
joints in the hands and feet are loose. The skin is thin and
translucent, with veins dramatically visible. The skin bruises
easily. Other complications can include collapsed lungs, premature
aging of the skin on the hands and feet, formation of openings
between arteries and veins, and complications following surgery. Ehlers Danlos Syndrome
vascular type is inherited in an autosomal dominant manner.
Kyphoscoliosis type
The major symptoms of kyphoscoliosis type, formerly called Ehlers Danlos Syndrome type
VI, are general joint looseness. At birth, the muscle tone is poor,
and motor skill development is delayed. Also, infants with this type
of Ehlers Danlos Syndrome have an abnormal curvature of the spine (scoliosis). The
scoliosis becomes progressively worse with age to the point that the
individual may no longer be able to walk by age 20. The eye and skin
are fragile and easily damaged, and blood vessel involvement is a
possibility. The bones may also be affected as demonstrated by a
decreased amount of bone tissue. Kyphoscoliosis type is inherited in
an autosomal recessive manner.
Arthrochalasia type
Dislocation of the hip joint typically accompanies arthrochalasia
type Ehlers Danlos Syndrome, formerly called Ehlers Danlos Syndrome type VIIB. Other joints are also
unusually loose, leading to recurrent partial and total
dislocations. The skin has a high degree of stretchability and
bruises easily. Individuals with this type of Ehlers Danlos Syndrome may also
experience mildly diminished bone mass, scoliosis, and poor muscle
tone. Arthrochalasia type is inherited in an autosomal dominant
manner.
Dermatosparaxis type
Individuals with this type of Ehlers Danlos Syndrome, once called type VIIC, have
extremely fragile skin that bruises easily but does not scar
excessively. The skin is soft and may sag, leading to an aged
appearance even in young adults. Individuals may also experience
hernias. Dermatospraraxis type is inherited in an autosomal
recessive manner.
Other types
Certain Ehlers Danlos Syndrome types have retained their original classifications owing
to their rarity and a lack of complete information. |