Arthrogryposis Multiplex Congenita

INTRODUCTION:-

Arthrogryposis, also known as Arthrogryposis Multiplex Congenita, is a rare congenital disorder that causes multiple joint contractures and can include muscle weakness and fibrosis. It is a non-progressive disease. There are many known subgroups of AMC, with differing signs, symptoms, causes etc.. In some cases, few joints may be affected and may have a nearly full range of motion. 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

Intelligence is relatively normal

Signs and symptoms:-

  • Deformities are prominent at birth. AMC is not progressive; however, the condition that causes it (eg, muscular dystrophy) may be. Affected joints are contracted in flexion or extension.The shoulder (internal rotation), elbow (extension and pronation), wrist (volar and ulnar), hand (fingers in fixed flexion and thumb-in-palm), hip (flexed, abducted and externally rotated, often dislocated), knee (flexion) and foot (clubfoot).
  • Leg muscles are usually hypoplastic, and limbs tend to be tubular and featureless.
  • Soft-tissue webbing sometimes occurs over ventral aspects of the flexed joints.
  • The spine may be scoliotic.
  • lung hypoplasia with associated respiratory problems
  • growth retardation,
  • midfacial hemangioma,
  • facial and jaw variations, and abdominal hernias.
  • Leg muscles are usually hypoplastic, and limbs tend to be tubular and featureless.
  • Intelligence is usually unimpaired or mildly abnormal.

Causes

The cause is unknown[7], although several mechanisms have been suggested. This includes decreasded fetal movements, hyperthermia of the fetus, prenatal virus, fetal vascular compromise, septum of the uterus, decreased amniotic fluid, muscle and connective tissue developmental abnormalities. [5][6] 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.[3][9]

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 - It is believed that the neuropathic form of AMC involves a deterioration in the anterior horn cell leading to muscle weakness and fibrosis. [46]Central nervous system and spinal cord are malformed. In these cases, a wide range of other conditions usually accompanies arthrogryposis. [6]
  • 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.[3][9]

CLINICAL FEATURES:-

Although joint contractures and associated clinical manifestations vary from case to case, several characteristics are common, including the following: 

  • Involved extremities are fusiform or cylindrical in shape, with thin subcutaneous tissue and absent skin creases.
  • Deformities are usually symmetric, and severity increases distally, with the hands and feet typically the most deformed.
  • Joint rigidity may be present.
  • The patient may have joint dislocation, especially the hips and, occasionally, the knees
  • Atrophy may be present, and muscles or muscle groups may be absent.
  • Sensation is usually intact, although deep tendon reflexes may be diminished or absent.

Contractures

  • Distal joints are affected more frequently than proximal joints.
  • Observe flexion versus extension, limitation of movement (fixed vs passive vs active), and characteristic position at rest; note the severity of all limitations. Distinguish between complete fusion or ankylosis and soft-tissue contracture.
  • Range of motion in the jaw is frequently limited.
  • Intrinsically derived contractures are frequently associated with polyhydramnios; the contractures are symmetric and accompanied by taut skin, pterygia across joints, and a lack of flexion creases. Recurrence risk and prognosis depend on etiology.
  • Extrinsically derived contractures are associated with positional limb anomalies, large ears, loose skin, and normal or exaggerated flexion creases. Patients have an excellent prognosis and a low recurrence risk.

Deformities

  • Limb deformities include pterygium, shortening, webs, compression (eg, due to cord wrapping), absent patella, dislocated radial heads, and dimples.
  • Facies deformities include asymmetry, flat nasal bridge, and hemangioma. Jaw deformities include micrognathia and trismus.
  • Other deformities include scoliosis, genital deformities (cryptorchidism, lack of labia, microphallus), and hernia (inguinal, umbilical).
  • Other features of the fetal akinesia sequence include intrauterine growth retardation, pulmonary hypoplasia, and craniofacial anomalies such as hypertelorism, cleft palate, depressed nasal tip, high nasal bridge, functional short gut with feeding problems, and short umbilical cord.
  • Absent or distorted crease abnormalities are a result of aberrant form or function in early hand or foot development.

Malformations

  • Craniofacial malformations may involve the CNS (structural malformations, seizures, mental retardation [MR]), skull (craniosynostosis, asymmetry, microencephaly), eyes (small and malformed eyes, corneal opacities, ptosis, strabismus), and palate (high, cleft, submucous cleft).
  • Respiratory problems include tracheal and laryngeal clefts and stenosis. Hypoplasia, weak muscles, or hypoplastic diaphragm may affect lung function.
  • Limb malformations include deletion anomalies, radioulnar synostosis, syndactyly, and shortened digits.
  • Skin vasculature abnormalities may cause hemangiomas and cutis marmorata; distal limbs may be blue and cold.
  • Cardiac problems include congenital anomalies and cardiomyopathy.
  • The kidneys, ureters, and bladder may have structural anomalies.
  • Nervous system problems include loss of vigor; lethargy; slow, fast, or absent deep tendon reflexes; and sensory deficits.
  • Muscle malformations include decreased muscle mass, soft muscle texture, fibrous bands, abnormal tendon attachments, and muscle changes over time.

Connective tissue abnormalities

  • Skin webs (pterygia) across joints, with limitation of movement, are common. Skin dimples are common over joints where movement is limited.
  • Skin may be soft, doughy, thick, or extensible. Subcutaneous fat is decreased or increased. Inguinal, umbilical, or diaphragmatic hernias may be present. Thickness in joints, symphalangism, and abnormalities in tendon attachment and length may also be present.
  • Associated skin defects include scalp defects, amniotic bands on limbs, and nail defects
  • Pretibial linear skin indentation may be a sign of autosomal recessive inheritance or at least a sign for an increased risk of recurrence.

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.[5]

Treatment

As each person will respond differently, and will have different needs, a combination of therapies is beneficial.

Physical therapy including stretching (may include casting, splinting of affected joints), strengthening, and mobility training are often provided to improve flexion and range of motion to increase mobility. 

Occupational therapy can include training in ADL and fine motor skills as well as addressing psychosocial and emotional implications of living with a disability. Since there is a variety of mobility impairments, individually tailored orthopaedic correction is often beneficial.

Orthopedic surgery may be elected to correct severely affected joints and limbs and symptoms such as clubfoot, hernia repair and correction of unilateral hip dislocation, in cases where these surgeries improve quality of life.

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