AMC (Arthrogryposis Multiplex Congenita)

What is Arthrogryposis Multiplex Congenita (commonly called AMC)?

The word arthrogryposis comes from the Greek derived "arthro-", joint + "gryposis ", crooking. The word “multiplex” is a Latin derived word meaning “many” or “multiple” and “congenita” is a Latin derived word meaning “existing at or dating from birth”. Therefore, the term Arthrogryposis Multiplex Congenita can be loosely translated as "lots of crooked joints at birth." These joint contractures develop before birth (prenatally) and are evident at birth (congenitally). A newborn with arthrogryposis lacks the normal range of motion in one or more joints. It is really more of a description than a diagnosis, as most people have AMC as a result of another condition.

Which joints are affected by AMC?

Joints affected by AMC may include the jaw, spine, shoulders, elbows, wrists, fingers, hips, knees, ankles, feet and toes -- virtually any and all joints.

How does AMC affect the joints?

The range of motion in the joints of the arms and legs is usually limited or fixed. The impairment of joint mobility in AMC is often accompanied by overgrowth (proliferation) of fibrous tissue in the joints (fibrous ankylosis).

How does AMC develop?

In normal embryonic development, the joints begin to develop by about 5 to 6 weeks of gestation. There are joint spaces by 7 weeks, and the limbs can be seen moving by 8 weeks. This motion of joints is clearly essential to the proper development of the joints and structures around the joints. Limitation of fetal motion/joint motion before birth leads to joint contractures.

What causes limitation of joint motion before birth?

Prenatal limitation of joint mobility can result from:

Neurologic deficits: Including anencephaly, defects of the spine such as spina bifida (meningomyelocele), and nerve deficiencies.

Muscle deficits: Including failure of muscle development (agenesis of muscle), fetal diseases of muscle (fetal myopathy)

Connective tissue and skeletal defects: Including fusion of bones (synostosis), failure of a joint to develop, prenatal fixation of a joint, excess laxity and of dislocation of joints, and fixation of soft tissue around the joint.

Fetal crowding or constraint: Fetal crowding occurs when there is not enough room for the fetus to move around freely in multiple births. Fetal constraint occurs from lack of amniotic fluid (oligohydramnios) due to underproduction of fluid by the fetal kidneys, failure of the fetus to swallow and recirculate the fluid, or chronic leakage of fluid from the uterus.

Maternal disorders: Maternal neuromuscular disorders of myotonic dystrophy, and myasthenia gravis. Maternal use of drugs, maternal infections, and maternal trauma. There is also evolving evidence that maternal multiple sclerosis can be a contributing factor to AMC.

Are there different types of AMC?

AMC is a sign associated with many specific conditions and syndromes. It can be seen in isolation or it can be seen in association with other congenital abnormalities as part of a condition or syndrome.

The basic classification divides affected children into those who:

• have only limb involvement
• have limb and trunk involvement
• have craniofacial or visceral involvement
• have severe central nervous system dysfunction.

How is the type of AMC determined?

The type of AMC is determined by the pattern of contractures, as well as other diagnostic tests. The physician will answer questions such as: are the contractures symmetrical? Are they only in the hands and feet? Are there malformations in other body parts? An MRI of the brain is usually done to rule-out neurological involvement. A muscle biopsy may be done to determine the extent of the fibrosis of the muscles and look at their cellular structure. Chromosomal and DNA testing may be done. Not everyone with AMC has all of these tests, because some types can be ruled out just by observing the contractures and the muscle movement. Ruling-out or ruling-in various conditions is called “differential diagnosis”. At times, two medical conditions have similar presentations; for instance, amyoplasia and Bilateral Brachial Plexus Palsy look the same at first glance, but only BBPP shows the abnormal posture when the muscles are active. It is important for you to understand the type of AMC your child has and how your doctor came to the diagnosis; don’t be afraid to seek a second opinion.

What is a Geneticist?

You may be referred to a geneticist when the baby is born, or earlier if AMC is suspected while you are pregnant. Geneticists are specialists who know about all the little details that determine what particular kind of condition a child has. Things like ear shape, closeness of the eyes, length of the arms, all help to make a diagnosis. Proper diagnosis is important, because if there is an underlying genetic cause of AMC, the prognosis and treatments might be changed. You should be aware that there is a difference between a clinical geneticist, who is a physician with special training in genetics, and a genetic counsellor, who holds a master's degree.

Is AMC fatal?

The life span of affected individuals depends on the disease severity and associated malformations but is usually normal. Lethal forms of AMC are reported and often cause miscarriage, stillbirth, or neonatal death. When this occurs, it is because the malformations are so severe they make it impossible for the child to live. About 50% of patients with limb involvement and central nervous system dysfunction die in the first year of life. Scoliosis may also compromise respiratory function. Infants born with AMC should have their respiratory status evaluated closely if they encounter an upper respiratory infection, the underdeveloped chest/abdomen muscles and/or spinal deformities can compromise an infant’s ability to manage the congestion involved with an upper respiratory infection.

Does AMC get better?

AMC is considered a non-progressive disorder; this means that it will not get worse with age. The joint contractures that are present will not get worse than they are at the time of birth. In fact, with physical therapy, the contractures frequently improve dramatically! Surgery, stretching, range of motion and physical therapy are currently the cornerstone in management of AMC. Joint contractures can be difficult to manage and you may, at times, experience regression of gains that have been made. Regression of gains made through surgery, physical therapy and stretching is a common occurrence and happens because as the child with AMC grows the connective tissues may not be able to lengthen at the same rate as the child’s growth causing joint contractures to recur. With proper treatment, most children can make significant improvements in their activities of daily life, and live relatively normal lives.

How do you treat AMC?

Treatment consists primarily of surgery, stretching, physical therapy, joint range-of-motion (ROM) and braces/splinting. Surgery is utilized to release contracted tissues and improve joint position. Stretching can be achieved by serial casting, which involves repeated stretching and casting. A method called the Ponseti Method is a common approach to managing club-foot associated with AMC. Splinting and bracing is used to maintain joint position, often with custom-made splints/braces.

Are there any problems they have that I can’t see?

Individuals with AMC frequently require surgical procedures to help correct joint deformities. The caregivers of a child with AMC should be aware that there can be problems associated with the administration of anaesthesia during these surgical procedures. If the child has facial or spinal deformities intubation can be difficult or impossible. Individuals with AMC are also more susceptible to the respiratory depressant effects of anaesthesia because of their muscle weakness, underdevelopment of the lungs or spinal deformities. It is important to inform the anaesthesiologist of your child’s diagnosis, even if the surgery has nothing to do with AMC.
The overall development of a child with AMC should be followed by a medical professional. Developmental skills such as fine motor skills, gross motor skills, oral and speech development and social development should be followed closely.

So what can and can’t people with AMC do?

This, again, depends on the severity of the individual’s condition. Some people have mild enough AMC that their physical activities are limited only slightly, while others may need assistance to perform daily activities. This assistance may be in the form of a wheelchair or even a personal aid. The abilities of a person with AMC are as varied as the presentations of AMC itself.

I found out my baby has AMC when she was born. How do I take care of her?

In most cases of AMC it is most beneficial to begin stretching and massage immediately—in the hospital if possible. If your doctor does not recommend immediate stretching, make sure you understand and agree to the reasons they give you. As always, don’t be afraid to seek a second opinion. Your baby may appear fragile to you, in most cases of AMC they are not, you will still love them and care for them as any other child.

Is assistance available for my child with AMC?

Your child will almost certainly qualify for Early Intervention programs, and may also qualify for financial medical assistance. Talk to a hospital social worker, who can direct you to the appropriate programs. If you are out of the hospital, call your local Department of Health, and they should be able to direct you. Programs vary widely from one state to another. It is to your benefit to educate yourself to the programs and assistance that are available to you and your child in your area.

Can people with AMC have kids?

It is recommended that an adult with AMC whom is planning to have a child seek advice from a medical professional.

Medical information obtained from our website is not intended as a substitute for professional care. If you have or suspect you have a problem, you should consult a healthcare provider.

More information available at http://www.amcsupport.org

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