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There is no single factor that is consistently found in the prenatal history of individuals affected with amyoplasia and, in some cases, there is no known cause of the disorder.
Amyoplasia is a sporadic condition that occurs due to lack of fetal movement in the womb. There is no specific gene that is known to cause the disorder. It is thought to be multifactorial, meaning that numerous genes and environmental factors play a role in its development. The recurrence risk is minimal for siblings or children of affected individuals. There have been no reports of recurrent cases of amyoplasia in a family.
The fetal akinesia in amyoplasia is thought to be caused by various maternal and fetal abnormalities. In some cases, the mother's uterus does not allow for adequate fetal movement because of a lack of amniotic fluid, known as oligohydramnios, or an abnormal shape to the uterus, called a bicornuate uterus.
There may also be a myogenic cause to the fetal akinesia, meaning that fetal muscles do not develop properly due to a muscle disease (for example, a congenital muscular dystrophy). Similarly, connective tissue tendon and skeletal defects may contribute to the fetal akinesia and be the primary cause of amyoplasia. Additionally, malformations may occur in the central nervous system and/or spinal cord that can lead to a lack of fetal movement in utero. This neurogenic cause is often accompanied by a wide range of other conditions. Other causes of fetal akinesia may include a maternal fever during pregnancy or a virus.
The frequency of this disorder is unknown, but it is very rare. Only a few families with the condition have been reported.
Arthrogryposis could also be caused by intrinsic factors. This includes molecular, muscle- and connective tissue development disorders or neurological abnormalities.
70-80% of the cases of the most severe forms of arthrogryposis are caused by neurological abnormalities, which can be either genetic or environmental.
The underlying aetiology and pathogenesis of congenital contractures, particularly arthrogryposis and the mechanism of the mutations remains an active area of investigation. Because identifying these factors could help to develop treatment and congenital finding of arthrogryposis.
Surgery may be necessary to address the congenital deformities frequently occurring in conjunction with arthrogryposis. Surgery on feet, knees, hips, elbows and wrists may also be useful if more range of motion is needed after therapy has achieved maximum results. In some cases, tendon transfers can improve function. Congenital deformities of the feet, hips and spine may require surgical correction at or about one year of age.
Tetra-amelia syndrome has been reported in only a few families worldwide.
According to a 2011 study by Bermejo-Sanchez, amelia – that is, the lacking of one or more limbs – occurs in roughly 1 out of every 71,000 pregnancies.
It is one of a spectrum of skeletal disorders caused by mutations in the "SLC26A2" gene. The protein encoded by this gene is essential for the normal development of cartilage and for its conversion to bone. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, but in adulthood this tissue continues to cover and protect the ends of bones and is present in the nose and external ears. Mutations in the SLC26A2 gene alter the structure of developing cartilage, preventing bones from forming properly and resulting in the skeletal problems characteristic of diastrophic dysplasia.
This condition is an autosomal recessive disorder, meaning that the defective gene is located on an autosome, and both parents must carry one copy of the defective gene in order to have a child born with the disorder. The parents of a child with an autosomal recessive disorder are usually not affected by the disorder.
Acheiropodia (ACHP), also known as Horn-Kolb Syndrome, Acheiropody and Aleijadinhos (Brazilian type), is an autosomal recessive disorder that results in hemimelia, a lack of formation of the distal extremities.
This is a congenital defect which consists of bilateral amputations of the distal upper and lower extremities, as well as aplasia of the hands and feet. It was first discovered and is prevalent almost exclusively in Brazil.
Autosomal recessive multiple epiphyseal dysplasia (ARMED), also called epiphyseal dysplasia, multiple, 4 (EDM4), multiple epiphyseal dysplasia with clubfoot or –with bilayered patellae, is an autosomal recessive congenital disorder affecting cartilage and bone development. The disorder has relatively mild signs and symptoms, including joint pain, scoliosis, and malformations of the hands, feet, and knees.
Some affected individuals are born with an inward- and downward-turning foot (a clubfoot). An abnormality of the kneecap called a double-layered patella is also relatively common. Although some people with recessive multiple epiphyseal dysplasia have short stature as adults, most are of normal height. The incidence is unknown as many cases are not diagnosed due to mild symptoms.
Medical conditions include frequent ear infection, hearing loss, hypotonia, developmental problems, respiratory problems, eating difficulties, light sensitivity, and esophageal reflux.
Data on fertility and the development of secondary sex characteristics is relatively sparse. It has been reported that both male and female patients have had children. Males who have reproduced have all had the autosomal dominant form of the disorder; the fertility of those with the recessive variant is unknown.
Researchers have also reported abnormalities in the renal tract of affected patients. Hydronephrosis is a relatively common condition, and researchers have theorized that this may lead to urinary tract infections. In addition, a number of patients have suffered from cystic dysplasia of the kidney.
A number of other conditions are often associated with Robinow syndrome. About 15% of reported patients suffer from congenital heart defects. Though there is no clear pattern, the most common conditions include pulmonary stenosis and atresia. In addition, though intelligence is generally normal, around 15% of patients show developmental delays.
Mutations in the "COL11A2" gene cause otospondylomegaepiphyseal dysplasia. The protein made by the "COL11A2" gene is involved in the production of type XI collagen. This type of collagen is important for the normal development of bone and other connective tissues. Mutations in the "COL11A2" gene lead to a loss of function of this type of collagen, resulting in the signs and symptoms of OSMED.
OSMED is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the defective gene - one from each parent - must be inherited for a person to be affected by the disorder. The parents of a child with an autosomal recessive disorder are usually not affected but are carriers of one copy of the altered gene. A recessive pattern of inheritance makes OSMED unique among the type II and type XI collagenopathies.
Mutations in the SLC26A2 (DTDST) gene, located at human chromosome 5q32-33.1, are the cause of ARMED. It is considered a milder disorder within a spectrum of skeletal disorders caused by mutations in the gene, which encodes a protein that is essential for the normal development of cartilage and its conversion to bone. Mutations in the SLC26A2 gene alter the structure of developing cartilage, preventing bones from forming properly and resulting in associated skeletal maldevelopment.
The disorder is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 5 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.
NPCA is a syndrome and can have diverse causes. It has a genetic basis and inheritance is considered to be autosomal recessive. However, autosomal dominant variety has also been reported. There may be familial balanced translocation t(8;20)(p22;q13) involved.
Achondrogenesis, type 1B is a severe autosomal recessive skeletal disorder, invariable fatal in the perinatal period. It is characterized by extremely short limbs, a narrow chest, and a prominent, rounded abdomen. The fingers and toes are short and the feet may be rotated inward. Affected infants frequently have a soft out-pouching around the belly-button (an umbilical hernia) or near the groin (an inguinal hernia).
Achondrogenesis, type 1B is a rare genetic disorder; its incidence is unknown. Achondrogenesis, type 1B is the most severe condition in a spectrum of skeletal disorders caused by mutations in the "SLC26A2" gene. This gene provides instructions for making a protein that is essential for the normal development of cartilage and for its conversion to bone. Mutations in the "SLC26A2" gene disrupt the structure of developing cartilage, preventing bones from forming properly and resulting in the skeletal problems characteristic of achondrogenesis, type 1B.
Achondrogenesis, type 1B is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.
Diastrophic dysplasia (DTD) is an autosomal recessive dysplasia which affects cartilage and bone development. ("Diastrophism" is a general word referring to a twisting.) Diastrophic dysplasia is due to mutations in the "SLC26A2" gene.
Affected individuals have short stature with very short arms and legs and joint problems that restrict mobility.
Non-progressive congenital ataxia (NPCA) is a non-progressive form of cerebellar ataxia which can occur with or without cerebellar hypoplasia.
Genetic studies have linked the autosomal recessive form of the disorder to the "ROR2" gene on position 9 of the long arm of chromosome 9. The gene is responsible for aspects of bone and cartilage growth. This same gene is involved in causing autosomal dominant brachydactyly B.
The autosomal dominant form has been linked to three genes - WNT5A, Segment polarity protein dishevelled homolog DVL-1 (DVL1) and Segment polarity protein dishevelled homolog DVL-3 (DVL3). This form is often caused by new mutations and is generally less severe then the recessive form. Two further genes have been linked to this disorder - Frizzled-2 (FZD2) and Nucleoredoxin (NXN gene). All of these genes belong to the same metabolic pathway - the WNT system. This system is involved in secretion for various compounds both in the fetus and in the adult.
A fetal ultrasound can offer prenatal diagnosis 19 weeks into pregnancy. However, the characteristics of a fetus suffering from the milder dominant form may not always be easy to differentiate from a more serious recessive case. Genetic counseling is an option given the availability of a family history.
Many features of gerodermia osteodysplastica (GO) and another autosomal recessive form of cutis laxa, wrinkly skin syndrome (WSS, ""), are similar to such an extent that both disorders were believed to be variable phenotypes of a single disorder.
Several delineating factors, however, suggest that gerodermia osteodysplastica and wrinkly skin syndrome are distinct entities, but share the same clinic spectrum.
While the prevailing feature of wrinkly, loose skin is more localized with GO, it is usually systemic, yet eases in severity with age during the course of WSS. Also, as the fontanelles ("soft spots") are usually normal on the heads of infants with GO, they are often enlarged in WSS infants.
While WSS is associated with mutations of genes on chromosomes 2, 5, 7, 11 and 14; GO has been linked to mutations in the protein GORAB. A serum sialotransferrin type 2 pattern, also observed with WSS, is not present in GO patients.
But perhaps the most notable feature, differentiating GO from WSS and similar cutis laxa disorders, is the age-specific metaphyseal peg sometimes found in GO-affected long bone, near the knee. Not appearing until around age 4–5, then disappearing by physeal closure, this oddity of bone is thought to represent a specific genetic marker unique to GO and its effects on bone development.
EEM syndrome (or Ectodermal dysplasia, Ectrodactyly and Macular dystrophy syndrome) is an autosomal recessive congenital malformation disorder affecting tissues associated with the ectoderm (skin, hair, nails, teeth), and also the hands, feet and eyes.
Gillespie syndrome, also called aniridia, cerebellar ataxia and mental deficiency. is a rare genetic disorder. The disorder is characterized by partial aniridia (meaning that part of the iris is missing), ataxia (motor and coordination problems), and, in most cases, intellectual disability. It is heterogeneous, inherited in either an autosomal dominant or autosomal recessive manner. Gillespie syndrome was first described by American ophthalmologist Fredrick Gillespie in 1965.
Tetra-amelia syndrome ("" + "amelia"), also called autosomal recessive tetraamelia, is an extremely rare autosomal recessive congenital disorder characterized by the absence of all four limbs. Other areas of the body are also affected by malformations, such as the face, skull, reproductive organs, anus and pelvis. The disorder is caused by mutations in the WNT3 gene.
It has been suggested that AMS is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.
Ablepharon macrostomia syndrome (AMS) is an extremely rare autosomal recessive genetic disorder characterized by malformations of the skull, skin, fingers and genitals. Affected individuals may also have malformations of the nipples and abdominal wall.
Younger individuals might experience language difficulties, and in some instances mental retardation is known.
In most cases, between the age of 2 and 4 oculomotor signals are present. Between the age of 2 and 8, telangiectasias appears. Usually by the age of 10 the child needs a wheel chair. Individuals with autosomal recessive cerebellum ataxia usually survive till their 20s; in some cases individuals have survived till their 40s or 50s.
Cenani–Lenz syndactylism, also known as Cenani–Lenz syndrome or Cenani–syndactylism, is an autosomal recessive congenital malformation syndrome involving both upper and lower extremities.