Arthrogryposis
From Biocrawler, the free encyclopedia.
Arthrogryposis (Arthrogryposis Multiplex Congenita) is a muscle disorder that causes multiple joint contractures at birth. A contracture is a limitation in the range of motion of a joint.
In some cases, few joints may be affected and the range of motion may be nearly normal. In the "classic" case of arthrogryposis, hands, wrists, elbows, shoulders, hips, feet and knees are affected. In the most severe cases, nearly every body joint may be involved, including the jaw and back. Frequently, the contractures are accompanied by muscle weakness, which further limits movement. Arthrogryposis is relatively rare, occurring in approximately one in 3,000 births.
In most cases, arthrogryposis is not a genetic condition and does not occur more than once in a family. In about 30% of the cases, a genetic cause can be identified. The risk of recurrence for these cases varies with the type of genetic disorder.
Research has shown that anything that prevents normal joint movement before birth can result in joint contractures. The joint itself may be normal. However, when a joint is not moved for a period of time, extra connective tissue tends to grow around it, fixing it in position. Lack of joint movement also means that tendons connecting to the joint are not stretched to their normal length; short tendons, in turn, make normal joint movement difficult. (This same kind of problem can develop after birth in joints that are immobilized for long periods of time in casts.)
In general, there are four causes for limitation of joint movement before birth:
- Muscles do not develop properly (atrophy). In most cases, the specific cause for muscular atrophy cannot be identified. Suspected causes include muscle diseases (for example, congenital muscular dystrophies), maternal fever during pregnancy, and viruses, which may damage cells that transmit nerve impulses to the muscles.
- There is not sufficient room in the uterus for normal movement. For example, the mother may lack a normal amount of amniotic fluid, or have an abnormally shaped uterus.
- Central nervous system and spinal cord are malformed. In these cases, a wide range of other conditions usually accompanies arthrogryposis.
- Tendons, bones, joints or joint linings may develop abnormally. For example, tendons may not be connected to the proper place in a joint.
