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Denouement and Discussion: Amyoplasia Congenita
Figure 1. The face is round with a midline glabellar nevus flammeus and upturned nose.
Figure 2. The shoulders are rounded, sloped, and internally rotated. The left elbow is extended with flexion contractures of the hand and wrist in a "policeman tip" position.
Arthrogryposis refers to fixed flexion contractures of a joint. The syndrome, arthrogryposis multiplex congenita, consists of a variety of disorders that result in the presence of fixed contractures of joints of the extremities at birth, with an estimated occurrence rate of 1 in 3000 births.1 Amyoplasia congenita is the most common cause of this syndrome, accounting for more than one third of cases of arthrogryposis.1
The limb findings in amyoplasia congenita are usually symmetric, involving all 4 extremities (84%), although some patients have isolated upper (11%) or lower (5%) extremity involvement.1 The arms are extended and the wrists and hands flexed, creating the so-called "policeman tip" position. The shoulders are sloped and rounded and internally rotated. The knees may be flexed or extended and the hips flexed and often dislocated. The feet are almost always in an equinovarus position. The muscle mass of the limbs is diminished, giving the extremities a slender appearance.
Facial features are not pathognomonic, although a round face with micrognathia and a small upturned nose are often present. A midline nevus flammeus of the forehead is present in three fourths of patients.1 Other abnormalities described in children with this disorder include cryptorchidism in males and labial abnormalities in girls, congenital hernias, abdominal wall defects, and scoliosis.
Pregnancy and birth history
A history of decreased fetal movement may be present. The amount of amniotic fluid may be increased, decreased, or normal. Intrauterine presentation is breech in almost one third of cases.1 Fractures of long bones are relatively common at birth, related to the immobility of joints and difficulty of delivery.
Based on the finding of decreased numbers of anterior horn cells in the spinal cord in the most common form of arthrogryposis, it has been postulated that hypotension in the developing fetal spinal cord at a time when the anterior horn cells are susceptible to insults may result in this form of the disorder.2,3 Amyoplasia congenita is sporadic in occurrence. No recurrences were reported in families of 135 affected patients.4
Histopathologic findings of muscle show replacement of muscle with adipose tissue and fibrous tissue. The remaining muscle shows variability in fiber diameter. Myopathic and neuropathic processes have been diagnosed from different muscles of the same patient.4 Results of electromyographic and nerve conduction velocity studies are also inconsistent. Electromyography may show a decreased or absent response to stimulation in some muscle tissues and a normal response in others.4 No structural or microscopic changes in the brain have been reported, but there is a reduction in the number and size of anterior horn cells at various spinal levels.4
Management and outcome
The prognosis of patients with amyoplasia congenita is relatively optimistic, although patients with markedly small limbs have a less favorable outcome. By age 5 years, 85% of children are ambulatory and completely independent in terms of activities of daily living.1 Primary goals in management are ambulation and maximum upper limb mobilization. Aggressive physical and occupational therapy beginning shortly after birth are key to good outcome. Educationally, almost all children function in regular classroom settings at the appropriate grade level, with only 4% in special programs.1 Amyoplasia congenita should be differentiated from congenital myopathies, myotonia congenita, and congenital muscular dystrophy, which have different clinical and pathologic pictures despite the presence of hypotonia and weakness.
Accepted for publication June 28, 2000.
Reprints: Naji A. Kulaylat, MD, Al-Hasa Specialty Services Division, Saudi Aramco Medical Services Organization, Box 6030, Mubarraz 31311, Kingdom of Saudi Arabia.
Picture of the Month. Arch Pediatr Adolesc Med. 2001;155(3):408. doi:10.1001/archpedi.155.3.407
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