出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/24 12:42:01」(JST)
| Dwarfism | |
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A man with dwarfism
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| Classification and external resources | |
| Specialty | Endocrinology, medical genetics |
| ICD-10 | E23.0, E34.2, E45.0, Q77.4 |
| ICD-9-CM | 253.3, 259.4 |
| DiseasesDB | 80 |
| MedlinePlus | 001176 |
| MeSH | D004392 |
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[edit on Wikidata]
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Dwarfism (UK: /ˈdwɔːfɪsəm/; US: /ˈdwɔːrfɪzəm/) occurs when an individual organism is short in stature resulting from a medical condition caused by slow growth. In humans, dwarfism is sometimes defined as an adult height of less than 4 feet 10 inches (58 in; 147 cm).[1] Dwarfism can be caused by more than 300 distinct medical conditions,[2] such that the symptoms and characteristics of individuals with dwarfism vary greatly. Disproportionate dwarfism is characterized by one or more body parts being relatively large or small in comparison to those of an average-sized adult, with growth variations in specific areas being apparent. In cases of proportionate dwarfism, the body appears normally proportioned, but is unusually small.
There is no single treatment for dwarfism. Individual differences, such as bone growth disorders, sometimes can be treated through surgery, some hormone disorders can be treated through medication, and by hormone replacement therapy; this treatment must be done before the child's growth plates fuse. Individual accommodations, such as specialized furniture, are often used by people with dwarfism.[3] Many support groups provide services to aid individuals with dwarfism and the discrimination they may face because of their dwarfism.[4]
For people, in addition to the medical aspect of the condition, there are social and sociological aspects as well. For a person with dwarfism, heightism can lead to ridicule in childhood and discrimination in adulthood.[5][6] In the United Kingdom, United States, Canada, Australia, and other English-speaking countries, some people with dwarfism prefer to be called little people.[7][8]
Historically, the term midget was used to describe "proportionate dwarfs"; however, this term is now regarded as offensive and pejorative[9] (see Terminology). Hypotonia, or low muscle tone, is common in dwarfs, but intelligence and lifespan are usually normal.
In men and women, the sole requirement for being considered a little person is having an adult height under 147 cm (4 ft 10 in) and it is almost always classified with respect to the underlying condition that is the cause of the short stature. Dwarfism is usually caused by a genetic variant; achondroplasia is caused by a mutation on chromosome 4. If dwarfism is caused by a medical disorder, the person is referred to by the underlying diagnosed disorder. Disorders causing dwarfism are often classified by proportionality. Disproportionate dwarfism describes disorders that cause unusual proportions of the body parts, while proportionate dwarfism results in a generally uniform stunting of the body.
Disorders that cause dwarfism may be classified according to one of hundreds of names, which are usually permutations of the following roots:
Examples include achondroplasia, osseous dysplasia, chondrodystrophy, and osteochondrodystrophy.[10]
A typical defining characteristic of dwarfism is an adult height of less than 147 cm (4 ft 10 in). Since those with dwarfism have such a wide range of physical characteristics, variations in individuals are identified by diagnosing and monitoring the underlying disorders.
Short stature can be inherited without any coexisting disease. Short stature in the absence of a medical condition is not generally considered dwarfism. For example, a short man and a short woman with average health will tend to produce children who are also short and with average health. While short parents tend to produce short children, persons with dwarfism may produce children of average height, if the cause of their dwarfism is not genetically transmissible or if the individual does not pass on the genetic variation.
Disproportionate dwarfism is characterized by one or more body parts being unusually large or small compared to the rest of the body. In achondroplasia one's trunk is usually of average size, one's limbs being proportionately shorter, one's head usually larger, and a prominent forehead.[11] In at least one case achondroplasia resulted in a significantly smaller trunk and head.[citation needed] Facial features are often affected and individual body parts may have problems associated with them. Orthopedic problems can result from multiple conditions such as diastrophic dysplasia and pseudoachondroplasia.
Proportionate dwarfism is marked by body parts being proportional but smaller.[12] Height is significantly below average and there may be long periods without any significant growth. Sexual development is often delayed or impaired into adulthood. Unlike disproportionate dwarfism, in some cases intellectual disability may be a part of proportionate dwarfism.
Physical maleffects of malformed bones vary according to the specific disease. Many involve joint pain caused by abnormal bone alignment, or from nerve compression.[7] Early degenerative joint disease, exaggerated lordosis or scoliosis, and constriction of spinal cord or nerve roots can cause pain and disability.[13] Reduced thoracic size can restrict lung growth and reduce pulmonary function. Some forms of dwarfism are associated with disordered function of other organs, such as the brain or liver, sometimes severely enough to be more of an impairment than the unusual bone growth.[14][15]
Mental effects also vary according to the specific underlying syndrome. In most cases of skeletal dysplasia, such as achondroplasia, mental function is not impaired.[12] However, there are syndromes which can affect the cranial structure and growth of the brain, severely impairing mental capacity. Unless the brain is directly affected by the underlying disorder, there is little to no chance of mental impairment that can be attributed to dwarfism.[16]
The psychosocial limitations of society may be more disabling than the physical symptoms, especially in childhood and adolescence, but people with dwarfism vary greatly in the degree to which social participation and emotional health are affected.
Dwarfism can result from myriad medical conditions, each with its own separate symptoms and causes. Extreme shortness in humans with proportional body parts usually has a hormonal cause, such as growth-hormone deficiency, once called pituitary dwarfism.[7][11] Two disorders, achondroplasia and growth hormone deficiency (also known as pituitary dwarfism), are responsible for the majority of human dwarfism cases.[2]
The most recognizable and most common form of dwarfism in humans is achondroplasia, which accounts for 70% of dwarfism cases, occurs in 4 to 15 out of 100,000 live births.[20]
It produces rhizomelic short limbs, increased spinal curvature, and distortion of skull growth. In achondroplasia the body's limbs are proportionately shorter than the trunk (abdominal area), with a larger head than average and characteristic facial features. Achondroplasia is an autosomal dominant disorder caused by the presence of a faulty allele in the genome. If a pair of achondroplasia alleles are present, the result is fatal. Achondroplasia is a mutation in the fibroblast growth factor receptor 3.[21] In the context of achondroplasia, this mutation causes FGFR3 to become constitutively active, inhibiting bone growth.[22]
Research by urologist Harry Fisch of the Male Reproductive Center at Columbia Presbyterian Hospital indicates that in humans this defect may be exclusively inherited from the father and becomes increasingly probable with paternal age: specifically males reproducing after 35.[23]
Growth hormone deficiency (GHD) is a medical condition in which the body produces insufficient growth hormone. Growth hormone, also called somatotropin, is a polypeptide hormone which stimulates growth and cell reproduction. If this hormone is lacking, stunted or even halted growth may become apparent. Children with this disorder may grow slowly and puberty may be delayed by several years or indefinitely. Growth hormone deficiency has no single definite cause. It can be caused by mutations of specific genes, damage to the pituitary gland, Turner's syndrome, poor nutrition,[24] or even stress (leading to psychogenic dwarfism). Laron syndrome (growth hormone insensitivity) is another cause.
Other causes of dwarfism are spondyloepiphyseal dysplasia congenita, diastrophic dysplasia, pseudoachondroplasia, hypochondroplasia, Noonan syndrome, primordial dwarfism, Turner syndrome, osteogenesis imperfecta (OI) and hypothyroidism. Severe shortness with skeletal distortion also occurs in several of the Mucopolysaccharidoses and other storage disorders.[25]
Serious chronic illnesses may produce dwarfism as a side effect. Harsh environmental conditions, such as malnutrition, may also produce dwarfism. These types of dwarfism are indirect consequences of the generally unhealthy or malnourished condition of the individual, and not of any specific disease. The dwarfism often takes the form of simple short stature, without any deformities. In societies where poor nutrition is widespread, the average height of the population may be reduced below its genetic potential by the lack of proper nutrition.
Dwarfism is often diagnosed in childhood on the basis of visible symptoms. A physical examination can usually suffice to diagnose certain types of dwarfism, but genetic testing and diagnostic imaging may be used to determine the exact condition.[26] In a person's youth, growth charts that track height can be used to diagnose subtle forms of dwarfism that have no other striking physical characteristics.[2]
Short stature or stunted growth during youth is usually what brings the condition to medical attention. Skeletal dysplasia is usually suspected because of obvious physical features (e.g., unusual configuration of face or shape of skull), because of an obviously affected parent, or because body measurements (arm span, upper to lower segment ratio) indicate disproportion.[26] Bone X-rays are often key to diagnosing a specific skeletal dysplasia, but are not the sole diagnostic tool. Most children with suspected skeletal dysplasias are referred to a genetics clinic for diagnostic confirmation and genetic counseling. Since about the year 2000, genetic tests for some of the specific disorders have become available.[27]
During an initial medical evaluation of shortness, the absence of disproportion and other clues listed above usually indicates causes other than bone dysplasias. Extreme shortness with completely normal proportions sometimes indicates growth hormone deficiency (pituitary dwarfism).[28]
Short stature alone, in the absence of any other abnormalities, may be the result of the distribution of offspring height from short-statured parents, rather than a symptom of any medical condition.[29]
Many types of dwarfism are currently impossible to prevent because they are genetically caused. Genetic conditions that cause dwarfism may be identified with genetic testing, by screening for the specific variation that result in the condition. However, due to the number of causes of dwarfism, it may be impossible to determine definitively if a child will be born with dwarfism.
Dwarfism resulting from malnutrition or a hormonal abnormality may be treated with an appropriate diet or hormonal therapy. Growth hormone deficiency may be remedied via injections of human growth hormone (HGH) during early life.
Genetic mutations of most forms of dwarfism caused by bone dysplasia cannot be altered yet, so therapeutic interventions are typically aimed at preventing or reducing pain or physical disability, increasing adult height, or mitigating psychosocial stresses and enhancing social adaptation.[4]
Forms of dwarfism associated with the endocrine system may be treated using hormonal therapy. If the cause is prepubescent hyposecretion of growth hormone, supplemental growth hormone may correct the abnormality. If the receptor for growth hormone is itself affected, the condition may prove harder to treat. Hypothyroidism is another possible cause of dwarfism that can be treated through hormonal therapy. Injections of thyroid hormone can mitigate the effects of the condition, but physical complications may be permanent.
Pain and disability may be ameliorated by physical therapy, braces or other orthotic devices, or by surgical procedures.[4] The only simple interventions that increase perceived adult height are dress enhancements, such as shoe lifts or hairstyle. Growth hormone is rarely used for shortness caused by bone dysplasias, since the height benefit is typically small (less than 5 cm [2 in]) and the cost high.[3] The most effective means of increasing adult height by several inches is distraction osteogenesis, though availability is limited and the cost is high in terms of money, discomfort, and disruption of life. Most people with dwarfism do not choose this option, and it remains controversial.[7] For other types of dwarfism, surgical treatment is not possible.
The appropriate term for describing a person of particularly short stature (or with the genetic condition achondroplasia) has historically been ambiguous, and has developed euphemistically over the past few centuries.
The noun dwarf stems from Old English dweorg, originally referring to a being from Germanic mythology—a dwarf—that dwells in mountains and in the earth, and is associated with wisdom, smithing, mining, and crafting. The etymology of the word dwarf is contested, and scholars have proposed varying theories about the origins of the being, including that dwarfs may have originated as nature spirits or as beings associated with death, or as a mixture of concepts. Competing etymologies include a basis in the Indo-European root *dheur- (meaning 'damage'), the Indo-European root *dhreugh (whence modern German Traum 'dream' and Trug 'deception'), and comparisons have been made with the Old Indian dhvaras (a type of demonic being). The being may not have gained associations with small stature until a later period.[30]
The terms "dwarf", "little person", "LP", and "person of short stature" are now generally considered acceptable by most people affected by these disorders.[11] However, the plural "dwarfs" as opposed to "dwarves" is generally preferred in the context of the medical condition, probably due to the fact that the plural "dwarves" was popularized by author J.R.R. Tolkien, describing a race of characters in his The Lord of the Rings books resembling Norse dwarves.[31]
"Midget", whose etymology indicates a "tiny biting insect",[32] came into prominence in the mid-19th century after Harriet Beecher Stowe used it in her novels Sunny Memories of Foreign Lands and Old Town Folks where she described children and an extremely short man, respectively.[11] Later some people of short stature considered the word to be offensive because it was the descriptive term applied to P. T. Barnum's dwarfs used for public amusement during the freak show era.[7][33] It is also not considered accurate as it is not a medical term or diagnosis, though it is sometimes used as a slang term to describe those who are particularly short, whether or not they have dwarfism.[34]
Dwarfs are supported to compete in sport by a number of organisations nationally and internationally.[35] The Dwarf Athletic Association of America.and the Dwarf Sports Association UK provide opportunities for dwarfs to compete nationally and internationally in the Americas and Europe respectively. The Dwarf Sports Association UK organises between 5 and 20 events per month for Athletes with restricted growth conditions in the UK[36]
In art, literature, and movies, dwarfs are rarely depicted as ordinary people who are very short but rather as a species apart. Novelists, artists, and moviemakers may attach special moral or aesthetic significance to their "apartness" or misshapenness.
Artistic representations of dwarfism can be found on Greek vases and other ancient artifacts, including ancient Egyptian art in which dwarfs are likely to have been seen as a divine manifestation, with records indicating they could reach high positions in society.[37][38]
The Bhagavat Purana Hindu text devotes nine chapters to the adventures of Vamana, a dwarf avatar of Lord Vishnu.
Depictions of dwarfism are also found in European paintings and many illustrations. Many European paintings (especially Spanish) of the 16th–19th centuries depict dwarfs by themselves or with others. In the Talmud, it is said that the second born son of the Egyptian Pharaoh of the Bible was a dwarf.[39] Recent scholarship has suggested that ancient Egyptians held dwarfs in high esteem.[40] Several important mythological figures of the North American Wyandot nation are portrayed as dwarfs.[41]
As popular media have become more widespread, the number of works depicting dwarfs have increased dramatically. Some feel that dwarf characters are often depicted based on the novelty factor of their stature rather than on other personal attributes. Dwarfism is depicted in many books, films, and TV series such as Willow, Austin Powers, Gulliver's Travels by Jonathan Swift,[42] The Wizard of Oz, Willy Wonka & the Chocolate Factory, A Son of the Circus, Little People Big World, The Little Couple, A Song of Ice and Fire (and its TV adaptation Game of Thrones), Seinfeld, The Orator, In Bruges, The Tin Drum by Günter Grass, the short-lived reality show The Littlest Groom, and the film The Station Agent.
The Animal Planet TV series Pit Boss features dwarf actor "Shorty" Rossi and his talent agency, "Shortywood Productions", which Rossi uses to provide funding for his pit bull rescue operation, "Shorty's Rescue". Rossi's three full-time employees, featured in the series, are all little people and aspiring actors.
In September 2014 Creative Business House along with Donnons Leur Une Chance created the International Dwarf Fashion Show to raise awareness and boost self-confidence of people living with dwarfism.[43]
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| Look up dwarf in Wiktionary, the free dictionary. |
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| リンク元 | 「dwarf」「microsomia」 |
| 拡張検索 | 「onanism」 |