Résumé :
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Amyoplasia (OMIM 108110) is the most common form of arthrogryposis multiplex congenita (AMC). It is a rare, sporadic condition characterized by decreased skeletal muscle mass, typical contractures and limb positioning at birth and normal intellectual development. Common associated findings are a round face with slightly small jaw and frontal midline capillary haemangioma. Typically, no other malformations are present. Pathogenesis is not yet very clear; it could be the consequence of myopathic, neuropathic or vascular abnormalities. We report a case of amyoplasia in a young girl. She is the 5th and last child of a non consanguineous couple. The pregnancy was considered as normal although the mother noted that foetal movements were poor. At birth the baby presented the characteristic contractures of four limbs with hardly any muscles mass in the four limbs. She also had on her round face a capillary haemangioma. She acquired head control and sitting position at normal age and her cognitive function at 6 years was completely normal. The MRI performed at 2 years confirmed that the muscles of the four limbs were replaced by a fibrous and fatty tissue whereas the paravertebral muscles had a normal signal. Muscle biopsies performed during club foot surgery showed very few muscle cells without organization in the right hallux abductor. This case of amyoplasia suggested a specific impairment of the appendicular muscles maturation contrasting with a normal maturation of the axial muscles. Work is in progress to test candidate genes involved in myoblaste proliferation and migration of limb’s buds. Key Words: Amyoplasia, arthrogryposis multiplex congenital, appendicular muscles, myogenic factors, myogenesis
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