What are differences between Arthrochalasia Type A and B of Ehlers-Danlos Syndrome?
Ehlers-Danlos Syndrome (EDS) is a rare group of genetic disorders of connective tissues that bind muscles, ligaments, organs and skin.
Arthrochalasia is defined as excessive looseness of joints in which the patient may be described as “double-jointed”.
In the Arthrochalasia type of EDS there is a mutation of either gene COL1A1 or COL1A2, resulting in arthrochalasia type A or type B, respectively. The gene is dominant such that it can be inherited from one parent, resulting in disease. More often, however, EDS occurs sporadically due to genetic mutation.
Patients with the Arthrochalasia type of EDS have skin hyperelasticity (redundant, easily stretched skin), Joint hyper-mobility, fragile tissues, easy bruising, poor muscle tone, kyphoscoliosis (abnormal curvature of the spine) and mild loss of bone density (osteopoenia) on X-ray examination of the skeleton. The arthrochalasia usually causes congenital (at birth) presence of dislocated hip(s), and a tendency for recurrent hip subluxations/dislocations later on. Subluxation means partial dislocation.
As a practical matter, there is little difference between Arthrochalasia Types A and B. Instead, the distinction is made on a genetic basis, depending on which of the collagen genes has mutated, or which abnormal collagen gene has been inherited.