Amyoplasia

Amyoplasia is a condition characterized by a generalized lack in the newborn of muscular development and growth, with contracture and deformity at most joints. It is the most common form of arthrogryposis. Amyoplasia is a condition characterized by a generalized lack in the newborn of muscular development and growth, with contracture and deformity at most joints. It is the most common form of arthrogryposis. It is characterized by the four limbs being involved, and by the replacement of skeletal muscle by dense fibrous and adipose tissue. Studies involving amyoplasia have revealed similar findings of the muscle tissue due to various causes including that seen in sacral agenesis and amyotrophic lateral sclerosis. So amyoplasia may also include an intermediate common pathway, rather than the primary cause of the contractors. Amyoplasia results when a fetus is unable to move sufficiently in the womb. Mothers of children with the disorder often report that their baby was abnormally still during the pregnancy. The lack of movement in utero (also known as fetal akinesia) allows extra connective tissue to form around the joints and, therefore, the joints become fixed. This extra connective tissue replaces muscle tissue, leading to weakness and giving a wasting appearance to the muscles. Additionally, due to the lack of fetal movement, the tendons that connect the muscles to bone are not able to stretch to their normal length and this contributes to the lack of joint mobility as well.