What is amyoplasia (classic arthrogryposis)?

Updated: Nov 11, 2020
  • Author: Mithilesh Kumar Lal, MD, MBBS, MRCP, FRCPCH, MRCPCH(UK); Chief Editor: Maria Descartes, MD  more...
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Disorders characterized mainly by limb involvement [13]

Amyoplasia (classic arthrogryposis) [8, 14]

This is characterized as follows:

  • The most common type of arthrogryposis seen in clinical practice and constitutes about one third of cases

  • The incidence is about 1 in 10,000 live births

  • Amyoplasia is a sporadic condition and has not been observed in siblings or offspring

  • The pathogenesis is thought to involve impaired blood circulation to the fetus early in pregnancy; hypotension and hypoxia damage the anterior horn cells, resulting in a lack or underdevelopment of muscle tissue, with fatty or connective tissue replacement

  • Symmetrical limb involvement is noted

  • The distinct positioning of the body includes internally rotated and adducted shoulders; fixed, extended elbows; pronated forearms; and flexed wrists and fingers

  • A severe talipes equinovarus deformity with either flexed or extended knees may be present

  • Hips may be flexed and externally rotated or extended and subluxated or dislocated

  • Characteristic midline facial hemangioma is often noted

  • Intelligence is normal

The natural history of untreated amyoplasia is largely undocumented and unknown. However, a study documented a 94% rate of survival for individuals with amyoplasia at 20 years. [4] Without treatment, the ambulatory and functional outcomes are poor.

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