Any condition that impairs the movement of the baby while in the womb can result in arthrogryposis multiplex congenita. Such causes may involve
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Limitation of the baby's movement, for example, because the mother's uterus is oddly shaped, she is carrying more than one baby, or the amniotic fluid is insufficient
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A disorder of the mother, such as multiple sclerosis
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A genetic disorder affecting the baby's ability to move while in the womb, such as muscular dystrophy or a connective tissue abnormality
More than 300 genetic disorders (such as spinal muscular atrophy type I and trisomy 18) have been associated with arthrogryposis multiplex congenita.
Symptoms
In infants with arthrogryposis multiplex congenita, a number of joints become curved and "frozen" and consequently cannot bend. Many infants have weakened muscles. Decreased movement of the baby's muscles and joints while in the womb likely cause the decreased movement of the joints after birth. Sometimes the nerves that would normally move the bones in the affected joints are also impaired. Infants with arthrogryposis may also have dislocated hips, knees, or elbows.
Diagnosis
Before birth, abnormal limbs may be seen during a routine ultrasound. If abnormal limbs are seen, doctors may do ultrasounds of other parts of the fetus's body or genetic testing on the fetus using chorionic villus sampling or amniocentesis. Doctors may recommend parents seek genetic counseling.
After birth, doctors do a physical examination and note the baby's frozen joints and limbs. Doctors then do genetic testing by analyzing a sample of the baby's blood to look for chromosome and gene abnormalities. This testing can help doctors determine whether a specific disorder is the cause and rule out other causes.
Tests of the muscles, such as a muscle biopsy (removal of a sample of muscle for examination) and electromyography (EMG), may be done to help doctors distinguish between various types of arthrogryposis.
Prognosis
Babies born with arthrogryposis typically develop relatively normal intelligence, except when the arthrogryposis is caused by a disorder or syndrome that also affects intelligence. Doctors seek to establish a specific diagnosis for what has caused the arthrogryposis so that parents know what the prognosis is and can receive genetic counseling.
Treatment
Placing the baby's limbs in a cast and doing physical therapy to carefully move and manipulate the stiff joints may improve joint movements.
Surgery may be needed to free the bones from attached tissue in order to have more normal joint movement. Surgically moving a muscle (for example, moving the triceps muscle so that it can flex rather than extend the elbow) may improve function.
