Arthrogryposis multiplex congenita

The exact cause of arthrogryposis multiplex congenita (AMC) is not fully understood. AMC is thought to be related to decreased fetal movement during development, which can occur for a variety of reasons. When a joint is not moved for a period of time, extra connective tissue may grow around it, fixing it in place. Lack of joint movement also means that tendons connected to the joint are not stretched to their normal length, which can make normal joint movement difficult.

In general, there are four causes for decreased fetal movement before birth:

1. Abnormal development of muscles. In most cases, the specific cause for this cannot be identified. Suspected causes include muscle diseases, maternal fever during pregnancy, and viruses which may damage the cells that transmit nerve impulses to the muscles.
2. Insufficient room in the uterus for normal movement. For example, multiple fetuses may be present, the mother may lack normal amounts of amniotic fluid or there may be uterine structural abnormalities.
3. Malformations of the central nervous system (the brain and/or spinal cord). In these cases, arthrogryposis is usually accompanied by a wide range of other symptoms.
4. Tendons, bones, joints or joint linings may develop abnormally. For example, tendons may not be connected to the proper place in a joint.

AMC can be a component of numerous condition caused by environmental factors, single gene changes (autosomal dominant, autosomal recessive, X-linked), chromosomal abnormalities and various syndromes.

The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Arthrogryposis multiplex congenita (AMC) is not inherited in most cases; however, a genetic cause can be identified in about 30% of affected people. It can be a component of many different genetic conditions, including those caused by a single gene change or a chromosomal abnormality, such as trisomy 18. Genetic conditions sometimes associated with AMC include some connective tissue disorders; muscle disorders such as muscular dystrophies or congenital myopathies; and certain mitochondrial disorders. Depending on the underlying genetic cause, it may be inherited in an autosomal recessive, autosomal dominant or X-linked manner. Some cases are thought to have multifactorial inheritance, which means that both genetic and environmental factors may play a role in causing the condition.

The long-term outlook (prognosis) for people with arthrogryposis multiplex congenita (AMC) depends on the severity of the condition, the underlying cause, and the affected person's response to therapy. The degree to which muscles and joints are affected varies significantly from person to person. AMC can be associated with a variety of conditions that are each characterized by unique symptoms.

In general, many people affected by AMC have a good prognosis. With physical therapy and other available treatments, substantial improvement in joint function and mobility is normally possible. Most people with AMC are of normal intelligence and are able to lead productive, independent lives as adults.

AMC affects approximately 1 in 3,000 individuals in the United States. The condition has been reported in individuals of Asian, African and European descent. It is more common in isolated populations such as Finland and the Bedouin community in Israel. The number of men and women affected is approximately equal.

The treatment of arthrogryposis multiplex congenita (AMC) varies based on the signs and symptoms present in each person and the severity of the condition. Early in life, physical therapy to stretch contractures can improve the range of motion of affected joints and prevent muscle atrophy. Splits can also be used in combination with these stretching exercises. For most types of arthrogryposis, physical and occupational therapy have proven very beneficial in improving muscle strength and increasing the range of motion of affected joints.

Some patients, however, have persistent functional difficulties despite a rigorous physical therapy regimen. In these cases, surgery may be recommended to achieve better positioning and increase the range of motion in certain joints. Rarely, tendon transfers have been done to improve muscle function.

Arthrogryposis Multiplex Congenita Support Inc. provides a listing of doctors and hospitals known for treating arthrogryposis multiplex congenita. Click on the link to access this list.

The American Association of Neuromuscular & Electrodiagnostic Medicine provides information about arthrogryposis multiplex congenita. Click on the link to view this information.