Arthrogryposis Multiplex Congenita (AMC)

What is Arthrogryposis Multiplex Congenita (AMC)?

Arthrogryposis multiplex congenita (AMC) is a group of disorders characterized by multiple joint contractures present at birth due to decreased fetal movement (fetal akinesia). The incidence is approximately 1 in 3,000 live births, and it results from various underlying neuromuscular or connective tissue abnormalities that impair joint mobility and muscle development in utero.

Causes

AMC occurs due to fetal akinesia, which prevents normal joint motion and leads to fibrosis, muscle shortening, and joint stiffness. Possible causes include:

• Neuromuscular disorders (e.g., spinal muscular atrophy, myopathies)
• Connective tissue disorders (e.g., Ehlers-Danlos syndrome, collagen abnormalities)
• Central nervous system abnormalities (e.g., brain malformations, neural tube defects)
• Maternal conditions (e.g., oligohydramnios, uterine anomalies, maternal myasthenia gravis)

Classification

AMC is classified based on its underlying cause and distribution of joint involvement:

1. Amyoplasia (Classic AMC) – The most common form, affecting both upper and lower limbs symmetrically. Often associated with clubfoot, internally rotated shoulders, and dislocated hips.
2. Distal Arthrogryposis – Primarily affects the hands and feet, often with an autosomal dominant inheritance pattern. Examples include Freeman-Sheldon syndrome and Sheldon-Hall syndrome.
3. Syndromic AMC – Associated with other systemic abnormalities, such as central nervous system or genetic syndromes (e.g., Larsen syndrome, Escobar syndrome).

Common Associations

• Clubfoot (talipes equinovarus) and other lower limb deformities
• Hip dislocations due to reduced fetal movement
• Scoliosis and spinal rigidity in severe cases
• Respiratory difficulties in syndromic cases with thoracic involvement
• Micrognathia and facial contractures in conditions like Freeman-Sheldon syndrome

Clinical Features

• Joint contractures (knees, elbows, wrists, fingers) leading to reduced mobility
• Cylindrical limbs with reduced muscle bulk
• Webbing of the skin across joints (pterygium)
• Normal intelligence in most cases, except when associated with central nervous system malformations

Evaluation and Treatment

Diagnosis is primarily clinical, supported by imaging studies:

• X-rays: Assess joint structure, hip dislocations, and scoliosis
• MRI/CT scan: Identify central nervous system anomalies if suspected
• Genetic testing: In cases with a suspected syndromic cause

Treatment aims to maximize function through:

• Physiotherapy and stretching to improve joint motion
• Splinting and serial casting for joint contractures
• Surgical interventions (e.g., tendon lengthening, osteotomies) in severe cases

Prognosis

The prognosis depends on the underlying cause and severity of joint involvement. With early intervention, many children achieve functional independence for daily activities. However, severe forms with respiratory or neurological involvement may have a guarded prognosis.

References

1. Bamshad M, et al. Arthrogryposis: A review and update. J Med Genet. 2009;46(9):677-685.
2. Hall JG. Arthrogryposis: A clinician’s guide. Semin Pediatr Neurol. 2015;22(1):30-37.
3. Hoffer MM, et al. Management of arthrogryposis. J Pediatr Orthop. 1983;3(3):293-299.