Arthrogryposis multiplex congenita

Arthrogryposis multiplex congenita (AMC), or simply arthrogryposis, describes congenital joint contracture in two or more areas of the body. It derives its name from Greek, literally meaning 'curving of joints' (arthron, 'joint'; grȳpōsis, late Latin form of late Greek grūpōsis, 'hooking'). Children born with one or more joint contractures have abnormal fibrosis of the muscle tissue causing muscle shortening, and therefore are unable to perform active extension and flexion in the affected joint or joints. Arthrogryposis multiplex congenita (AMC), or simply arthrogryposis, describes congenital joint contracture in two or more areas of the body. It derives its name from Greek, literally meaning 'curving of joints' (arthron, 'joint'; grȳpōsis, late Latin form of late Greek grūpōsis, 'hooking'). Children born with one or more joint contractures have abnormal fibrosis of the muscle tissue causing muscle shortening, and therefore are unable to perform active extension and flexion in the affected joint or joints. AMC has been divided into three groups: amyoplasia, distal arthrogryposis, and syndromic. Amyoplasia is characterized by severe joint contractures and muscle weakness. Distal arthrogryposis mainly involves the hands and feet. Types of arthrogryposis with a primary neurological or muscle disease belong to the syndromic group. Often, every joint in a patient with arthrogryposis is affected; in 84% all limbs are involved, in 11% only the legs, and in 4% only the arms are involved. Every joint in the body, when affected, displays typical signs and symptoms: for example, the shoulder (internal rotation); wrist (volar and ulnar); hand (fingers in fixed flexion and thumb in palm); hip (flexed, abducted and externally rotated, frequently dislocated); elbow (extension and pronation) and foot (clubfoot). Range of motion can be different between joints because of the different deviations. Some types of arthrogryposis like amyoplasia have a symmetrical joint/limb involvement, with normal sensations. The contractures in the joints can result in delayed walking development in the first 5 years, but severity of contractures do not necessarily predict eventual walking ability or inability. Intelligence is normal to above normal in children with amyoplasia, but it is not known how many of these children have an above normal intelligence, and there is no literature available about the cause of this syndrome. There are a few syndromes like the Freeman-Sheldon and Gordon syndrome, which have craniofacial involvement. The amyoplasia form of arthrogryposis is sometimes accompanied with a midline facial hemangioma.Arthrogryposis is not a diagnosis but a clinical finding, so this disease is often accompanied with other syndromes or diseases. These other diagnoses could affect any organ in a patient. There are a few slightly more common diagnoses such as pulmonary hypoplasia, cryptorchidism, congenital heart defects, tracheoesophageal fistulas, inguinal hernias, cleft palate, and eye abnormalities. Research of arthrogryposis has shown that anything that inhibits normal joint movement before birth can result in joint contractures. Arthrogryposis could be caused by genetic and environmental factors. In principle: any factor that curtails fetal movement can result in congenital contractures. The exact causes of arthrogryposis are unknown yet. The malformations of arthrogryposis can be secondary to environmental factors such as: decreased intrauterine movement, oligohydramnios (low volume or abnormal distribution of intrauterine fluid), and defects in the fetal blood supply. Other causes could be: hyperthermia, limb immobilization and viral infections. Myasthenia gravis of the mother leads also in rare cases to arthrogryposis. The major cause in humans is fetal akinesia. However, this is disputed lately. Arthrogryposis could also be caused by intrinsic factors. This includes molecular, muscle- and connective tissue development disorders or neurological abnormalities. Research has shown that there are more than 35 specific genetic disorders associated with arthrogryposis. Most of those mutations are missense, which means the mutation results in a different amino acid. Other mutations that could cause arthrogryposis are: single gene defects (X-linked recessive, autosomal recessive and autosomal dominant), mitochondrial defects and chromosomal disorders (for example: trisomy 18). This is mostly seen in distal arthrogryposis. Mutations in at least five genes (.mw-parser-output .smallcaps{font-variant:small-caps}TNN12, TNNT3, TPM2, MYH3 and MYH8) could cause distal arthrogryposis. There could be also connective tissue-, neurological of muscle development disorders. Loss of muscle mass with an imbalance of muscle power at the joint can lead to connective tissue abnormality. This leads to joint fixation and reduced fetal movement. Also muscle abnormalities could lead to a reduction of fetal movement.Those could be: dystrophy, myopathy and mitochondrial disorders. This is mostly the result of abnormal function of the dystrophin-glycoprotein-associated complex in the sarcolemma of skeletal muscles.