Arthrogryposis

Arthrogryposis, also known as Arthrogryposis Multiplex Congenita, is a rare congenital  disorder that causes multiple joint contractures and is characterized by muscle weakness and fibrosis. It is a non-progressive disease. The disease derives its name from Greek literally meaning 'curved or hooked joints'.

There are many known subgroups of AMC, with differing signs, symptoms, causes etc. . In some cases, few joints may be affected and the range of motion may be nearly normal. In the most common type of arthrogryposis, hands, wrists, elbows, shoulders, hips, feet and knees are affected. In the most severe types, nearly every joint is involved, including the jaw and back.

Frequently, the contractures are accompanied by muscle weakness, which further limits movement. AMC is typically symmetrical and involves all four extremities with some variation seen.

Classification
Some of the different types of AMC include:
 * Arthrogryposis multiplex due to muscular dystrophy.
 * Arthrogryposis ectodermal dysplasia other anomalies, also known as Cote Adamopoulos Pantelakis syndrome, Trichooculodermovertebral syndrome, TODV syndrome and Alves syndrome.
 * Arthrogryposis epileptic seizures migrational brain disorder.
 * Arthrogryposis IUGR thoracic dystrophy,also known as Van Bervliet syndrome.
 * Arthrogryposis like disorder, also known as Kuskokwim disease.
 * Arthrogryposis-like hand anomaly and sensorineural deafness.
 * Arthrogryposis multiplex congenita CNS calcification.
 * Arthrogryposis multiplex congenita distal (AMCD), with a large number of synonyms such as Arthrogryposis multiplex congenita, distal, x-linked (AMCX1) and Arthrogryposis spinal muscular atrophy
 * Gordon Syndrome, also known as Distal Arthrogryposis, Type 2A.
 * Arthrogryposis multiplex congenita, distal type 2B, also known as Freeman-Sheldon syndrome variant.
 * Arthrogryposis multiplex congenita neurogenic type (AMCN). This particular type of AMC has been linked to the AMCN gene on locus 5q35. Its mode of inheritance follows the Autosomal recessive patern.
 * Arthrogryposis multiplex congenita pulmonary hypoplasia, also with a large number of synonyms.
 * Arthrogryposis multiplex congenita whistling face, also known as Illum syndrome.
 * Arthrogryposis multiplex congenita, distal type 1 (AMCD1).
 * Arthrogryposis ophthalmoplegia retinopathy, also known as Oculomelic amyoplasia.
 * Arthrogryposis renal dysfunction cholestasis syndrome, also known as ARC Syndrome.

Signs and symptoms
There is a whole plethora of signs and symptoms for this group of diseases. Some of the more common signs and symptoms are associated with the shoulder (internal rotation deformity), elbow (extension and pronation deformity), wrist (volar and ulnar deformity), hand (fingers in fixed flexion and thumb-in-palm deformity), hip (flexed, abducted and externally rotated, often dislocated), knee (flexion deformity) and foot (clubfoot deformity). Complications may include scoliosis, lung hypoplasia leading to respiratory problems, growth retardation, midfacial hemangioma, facial and jaw deformities, respiratory problems, and abdominal hernias. Cognition and speech are usually normal.

Causes
The cause as such, is unknown though there have been several suggestions and factors suggested to play a role in AMC. This includes hyperthermia of the fetus, prenatal virus, fetal vascular compromise, septum of the uterus, decreased amniotic fluid, muscle and connective tissue developmental abnormalities. In general, the causes can be classified into extrinsic and intrinsic factors.

Extrinsic

 * There is insufficient room in the uterus for normal movement. For example, fetal crowding; the mother may lack a normal amount of amniotic fluid or have an abnormally shaped uterus.

Intrinsic

 * Musculoskeletal/Neuromuscular - Muscles do not develop properly (atrophy). In most cases, the specific cause for muscular atrophy cannot be identified. Suspected causes include muscle diseases (for example, congenital muscular dystrophies), maternal fever during pregnancy, and viruses, which may damage cells that transmit nerve impulses to the muscles.
 * Neurological - Central nervous system and spinal cord are malformed. In these cases, a wide range of other conditions usually accompanies arthrogryposis.
 * Connective Tissue - Tendons, bones, joints or joint linings may develop abnormally. For example, tendons may not be connected to the proper place in a joint.

Research has shown that anything that prevents normal joint movement before birth can result in joint contractures. The joint itself may be normal. However, when a joint is not moved for a period of time, extra connective tissue tends to grow around it, fixing it in position. Lack of joint movement also means that tendons connecting to the joint are not stretched to their normal length; short tendons, in turn, make normal joint movement difficult. (This same kind of problem can develop after birth in joints that are immobilized for long periods of time in casts.)

The principal cause of AMC is believed to be decreased fetal movements (akinesia) caused by maternal or fetal abnormalities. It is associated with neurogenic and myopathic disorders. It is believed that the neuropathic form of AMC involves a deterioration in the anterior horn cell leading to muscle weakness and fibrosis. In most cases, arthrogryposis is not a genetic condition and does not occur more than once in a family. In about 30% of the cases, a genetic cause can be identified. The risk of recurrence for these cases varies with the type of genetic disorder. There is a rare autosomal recessive form of the disease known to exist.

Diagnosis
To date, no prenatal diagnostic tools are available to test for the condition. Diagnosis is only used to rule out other causes. This is done by undertaking muscle biopsies, blood tests and general clinical findings rule out other disorders and provides evidence for AMC.

Treatment
While there is no cure, symptoms and deformities may still be alleviated with various methods due to multiple contractures and weakness. Physical therapy intervention including stretching (may include casting and splinting program of affected joints), strengthening, mobility training, are undertaken to improve flexion and range of motion. Occupational therapy interventions can include training in ADL and fine motor skills as well as addressing psychosocial and emotional implications of a chronic condition. Since there is a variety of different deformities, individually tailored orthopaedic correction is needed. Orthopedic surgery is usually needed to correct severely affected joints and limbs and symptoms such as clubfoot, hernia repair and correction if unilateral hip dislocation occurs.

Prognosis
Individuals with AMC require vigorous therapy and surgical intervention. This however depends on severity. Since AMC is not a progressive disorder though, there are also positive factors as well including normal cognition and speech and a potential for functional mobility leading to a productive and independent lifestyle, adapting to specific situations as required by the individuals particular symptom.

Epidemiology
AMC is relatively rare occurring in 1 out of every 3,000 live births. Amyoplasia, characterized by fatty and fibrous tissue replacement of the limb muscles, is the most common form 43%. The majority of affected individuals survive but a minority die, usually due to respiratory muscle involvement.