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What is Arthrogryposis Multiplex Congenita (AMC)?

Arthrogryposis Multiplex Congenita (AMC) is a term used to describe over 300 conditions that cause multiple curved joints in areas of the body at birth.  It varies from person to person with the commonality being stiff joints and muscle weakness. 

AMC is not a specific diagnosis but rather a clinical finding of permanent shortening of joints also referred to as non-progressive congenital contractures.

AMC is non-progressive meaning that the lack of movement, does not get worse as time goes by however, it is recommended that people affected seek advice to potentially prevent further impediments of the joints.

Occasionally AMC can also affect the central nervous system of which the survival rate can be low.

Causes of Arthrogryposis Multiplex Congenita (AMC)

Arthrogryposis Multiplex Congenita (AMC) is not a result of a problem in the formation of the joints, but rather with the development of the connective tissues around them that occurs after 8-10 weeks of pregnancy.

In AMC, this tissue fuses a joint in place, severely restricting movement in the areas affected which leads to the tendons around the affected joint being unable to stretch to their normal length. When there is limited movement for several months, this can also lead to joint contractures.

There are many causes of Arthrogryposis Multiplex Congenita (AMC) some of which are inherited. These are:

Abnormalities of connective tissue where the tendons, bones, joint or joint lining, develop in such a way that normal movement cannot occur in the womb.

Limited space or restricted movement in the womb such as with multiple births. In other cases there may be a lack of the normal level of amniotic fluid or the mother may have an abnormal shape to the womb that does not allow the baby to move freely.

Abnormalities of the muscle structure or function also known as myopathic processes this is where the muscles fail to form or do develop but do not function properly.

Abnormalities of the nerves that connect to the muscles also known as neuropathic processes this is where the nerves fail to form, mature or to function properly leading to a very severe lack of movement and often accompanies structural abnormalities.

Vascular compromise leading to loss of neurons – this is where there is a problem with the blood circulating normally which then fails to nourish the nerves leading to the muscles or the bones that make up the joint.

Maternal illness – a number of maternal metabolic disorders and maternal illness have been associated with the presence of multiple congenital contractures in the baby.

Types of Arthrogryposis Multiplex Congenita (AMC)

There are more than 300 conditions that come under the Arthrogryposis ‘umbrella’ and these can be divided into  three groups:

  • disorders with mainly limbs
  • disorders with limb plus some other body area e.g. cleft palate, the heart, intestinal defects, curvature of the spine
  • disorders with limb  and the central nervous system

Mainly limb

Amyoplasia is the most common type of the condition and is known as ‘classical Arthrogryposis’.  It occurs in 1 in every 10,000 live births and represents one third of all cases of people diagnosed with Arthrogryposis.  Usually people are affected in all four limbs but there are cases where only a person’s legs or arms are involved .  About 10% of people with Amyoplasia have some type of intestine or abdominal wall abnormality but this responds well to early physical therapy.

It is not seen as a genetic condition, but parents of a baby with Amyoplasia are advised to seek genetic counselling for their child as they approach adulthood.

With Distal Arthrogryposis Type I, it is the hands and feet that are usually the most severely affected. In a newborn baby, the characteristics of the disorder can clearly be seen as the hands are clenched and the fingers overlap.  Feet can also be affected along with the knees and hips but this is usually fairly mild.  Again, it has a relatively good response to early physical therapy.

This type has an autosomal dominant inheritance and, as only one parent must have an abnormal gene in order for the child to inherit the disease, there is a 50/50 chance of passing it on.

Limbs plus other body areas

Multiple Pterygium Syndromes

A pterygium is a winglike structure, web or triangular membrane that forms across a body joint. There are many types of pterygium syndrome but individuals with these conditions often have webs of skin at their neck, knees and elbows as well as multiple congenital contractures. Blood vessels and nerves run along the edge of this web and so much care is needed when operating.

Each of the different pterygium syndromes has a different form of inheritance.

Freeman Sheldon Syndrome (Whistling Face Syndrome)

As well as contractures of the hands and feet this condition also has facial involvement. The muscles are contracted in such a way as to give a ‘whistling’ appearance. In the most severe cases the mouth may have extremely limited movement. Even when the face is not so affected it might still be difficult for the individual to smile and there is often postnatal growth deficiency within this group.

Distal Arthrogryposis Type II B

This type of DA also has the features of paralysis to all or part of the eye and eyelids may appear droopy. As well as muscle weakness around the eyes, the eyes themselves may have limited movement, especially to the sides. Skin and muscles are hard and there is a lack of finger creases.

This type is autosomal dominant and quite common.

Distal Arthrogryposis Type II C

This type of DA also has the feature of a cleft lip.

Distal Arthrogryposis Type II D

With this type of DA there is also scoliosis (curvature of the spine).

Distal Arthrogryposis Type II E

This type of DA has a characteristic positioning of the hand in which the wrist is flexed but the metacarpalphalangeal joint (palm to wrist) is extended. There is limited opening of the jaw (trismus).

DA Type IIE is relatively common and does not run in families.

Limbs plus Central Nervous System

Babies in this category tend to do very poorly and may not survive. Sadly, this is usually quite obvious in the neonatal (first 28 days) and is not something that develops at a later stage.

Treatment of Arthrogryposis Multiplex Congenita (AMC)

Arthrogryposis is a diverse condition and no two people affected are alike.  However, through physiotherapy, selective use of surgery and orthoses (splints or callipers), the majority of children go on to lead full and active lives.

With every baby born with Arthrogryposis, it is important that an accurate diagnosis is sought as soon as possible.  A specific diagnosis will provide information about the prognosis, risk of recurrence as well as to guide health practitioners to the best therapies.  To help distinguish between the different types of Arthrogryposis, the doctors are likely to use all the diagnostic tools available and are likely to ask you about:

Family history

This is essential especially if there are other affected children in the family.  The doctor will look at paternal and maternal ages and ask about close marriages, known as consanguinity, in the family.

Prenatal history

Were there any maternal illness or fever, trauma or injury, any exposure to drugs, alcohol, medications that can cause birth defects?  Doctors will also specially ask about baby’s movement before the birth.

Birth history

This will include the length of the pregnancy and labour, time and length of delivery, position of the baby at birth and prenatal outcome.

The baby will undergo a series of tests to eliminate other distinct conditions and may include x-rays of spine, pelvis and the limbs; a muscle biopsy; MRI scans; a head scan as well as investigations on the central nervous system.

Physiotherapy

The success of repositioning joints and limbs through physiotherapy cannot be over emphasised.  During the first 3 to 4 months of life when the contractures tend to loosen significantly – known as the ‘Grace Period’ – some of the muscles that appear to be unusually weak may significantly increase in strength and bones tend to increase in mineralization and growth

Physiotherapy can usually be started even before a specific diagnosis has been determined.  By introducing an early programme of passive stretching while the baby’s tissues are still supple, it will help increase the range of movement in the stiff joints. This is often coupled with the use of splints to maintain a good position in the limb.  Parents should be taught the correct techniques so that they can continue therapy at home between hospital visits.  Often the use of serial plasters and corrective surgery later on in life complements this work and may help a child to stand and walk.  

Trick movements that they learn for themselves can often help children overcome difficulties they may have with their upper limbs.  If the aid of personalised equipment is needed an Occupational Therapist will be able to give help and advice.  

The majority of children with Arthrogryposis achieve some degree of mobility; either with the help of callipers, splints and crutches or completely independently.

Download more detailed advice on Physiotherapy for Children with Arthrogryposis from Mia Dunkley, Senior Paediatric Physiotherapist at Great Ormond Street Hospital, London.