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Types of Arthrogryposis

Arthrogryposis is described as the congenital non-progressive limitation of movement of two or more joints in different areas of the body.

Arthrogryposis takes its name from the Greek words: arthron, "joint"; gryposis, late Latin form of late Greek gruposis, "hooking." Arthrogryposis is typically looked at as a sign or symptom and not a definitive diagnosis.

There are many different types of AMC (in excess of 400) and in most cases the exact cause is unknown. However, all the different forms of AMC have one thing in common; the baby did not move his or her joints fully during pregnancy. This in turn can be caused by abnormal development of the spinal cord, muscles or nerves going to the muscles. The most common types of arthrogryposis are not hereditary and other types are individually very rare.

These conditions are typically divided into 3 groups:

• Arthrogryposis with mainly limb involvement
• Arthrogryposis with limb involvement and involvement with some other body area(s)
• Arthrogryposis with limb involvement and dysfunction of the central nervous system.

Arthrogryposis with mainly limb involvement

The most common type of Arthrogryposis is Amyoplasia. "A" meaning no, "myo" meaning muscle, and "plasia" meaning growth. It was recognized in 1980 as a specific form and is still the most prevalent form today. Amyoplasia is what orthopedic doctors typically refer to as "classical Arthrogryposis." Amyoplasia occurs at an incidence of 1 in 10,000 live births and seems to be exceptionally present in one of monozygotic twins. This increase in incidence is also noticeable among infants who had a "vanished" twin sibling, one who was recognized and then lost during pregnancy. Amyoplasia is typically characterized by limb involvement in all 4 limbs, severe equinovarus deformity of the feet, internally rotated shoulders, extended elbows, flexed wrists, and contractions of the fingers. Often times dimpling occurs over malformed joints and absent creasing in joints where creases would normally be expected. Babies with Amyoplasia are typically interactive, assertive, and display normal or higher than normal intelligence. Children with Amyoplasia are typically shorter than would normally be expected, following the 3rd - 5th percentile in growth charts. Amyoplasia is considered to be a sporadic condition and no reoccurrence has been observed in either siblings or offspring. Amyoplasia can occur in either only the lower limbs or only the upper limbs as well.

Another type of Arthrogryposis with mainly limb involvement is Distal type 1. Distal Arthrogryposis is characterized by medially overlapping fingers, clenched fists, ulnar deviation of fingers, contractions of the fingers, as well as other contractures of the hands and feet. Typically "distal" parts of the body are most severely affected with knees and hips sometimes being involved, but less severe, and the sparing of other joints within the body. All anomalies are orthopedic and these individuals are usually quite responsive to therapy. Distal type 1 is inherited through an autosomal dominant trait with variable expression. 8 different genes have been identified primarily mapped to chromosome 9.

Contractural Arachnodactyly, commonly known as Beal's Syndrome, is classified as Distal Arthrogryposis IIE. It is very similar in presentation to Marfan's Syndrome, but does not include any cardiovascular or ocular problems. Individuals with Contractural Arachnodactyly are typically long and thin. They often present with a "crumpled ear" in addition to multiple joint contractures. Contractural Arachnodactyly is also an autosomal dominant trait and has been associated with the fibrillin gene on chromosome 5.

Arthrogryposis involving limbs and other areas of the body

There are many types of Pterygium syndromes. A pterygium is a wing like structure, web, or triangular membrane that forms across a body joint. Individuals with pterygium syndromes often have webs of skin at their neck, knees, and elbows, as well as multiple congenital contractures. Different forms of Pterygium syndromes have different inheritance, some being recessive and some being dominant and occur on different genes. There are several types of lethal pterygium syndromes that are incompatible with life. A common form of Multiple Pterygium Syndrome is the Escobar type. Individuals with Multiple Pterygium Syndrome Escobar type often present with cervical vertebral anomalies, hands involved, chin-sternum ptergyia, and dysmorphic faces. In recent studies, maternal antibodies against embryonic neurotransmitters lead to increasing contractures with each pregnancy. Multiple Pterygium Syndromes including Escobar type have been found to be due to mutations in the subunits of the embryonic ACh receptors.

Freeman-Sheldon Syndrome (Whistling Face), which is also a type of Distal Arthrogryposis Type IIE, also affects the limbs and other areas of the body. Individuals with whistling face syndrome have a full forehead and masklike faces with a small mouth giving a whistling face appearance. These individuals often also present with a wide number of other symptoms such as kyphosis, post-natal growth deficiency, inguinal hernias, incomplete descent of the testes, and flexion of fingers, equinovarus feet with contracted toes, kyphosis, and scoliosis. Osteochondrodysplasia is another type of Arthrogryposis which affects the limbs and other areas of the body. Individuals with Osteochondrodysplasia exhibit both disproportionate short stature and characteristics of Arthrogryposis.

Distal Arthrogryposis Type IIB is another type of Arthrogryposis involving limbs and additional parts of the body. Individuals affected by Distal Type IIB often present with firm feeling muscles, thickened skin, and decreased eye movements also known as Ophthalmoplegia. This is also an autosomal dominant condition.

Arthrogryposis involving limbs and central nervous system

Cerebrooculofacioskeletal (COFS) Syndrome is a degenerative disorder where nerve cells fail to mature properly. It is an autosomal recessive disorder. Infants with COFS often present with microcephaly, structural abnormalities of the brain, eye abnormalities, micro-gnathia, abnormal ears, hypotonia, and multiple congenital contractures. This syndrome is lethal.

Restrictive Dermopathy is another syndrome in which the limbs and central nervous system are involved. In this case, skin does not grow normally during the fetal period and restricts in uterine growth. It is familial and inherited. This syndrome is lethal as well.

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