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Dwarfism (UK: ; US: ) occurs when an individual person or animal 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 . Dwarfism can be caused by more than 300 distinct medical conditions,〔(【引用サイトリンク】title=Dwarfism )〕 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. Many support groups provide services to aid individuals with dwarfism and the discrimination they may face because of their dwarfism. 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.〔(University of Pennsylvania, Arts and Sciences: "The Effect of Adolescent Experience on Labor Market Outcomes: The Case of Height" ).〕〔(Science Blog: "Short children more likely to be bullied at school" ).〕 In the United Kingdom, United States, Canada, Australia, and other English-speaking countries, some people with dwarfism prefer to be called little people.〔(【引用サイトリンク】url=http://www.littlepeopleuk.org/ )〕 Historically, the term midget was used to describe "proportionate dwarfs"; however, this term is now regarded as offensive and pejorative〔(''Merriam-Webster Dictionary'' Entry for midget: ''sometimes offensive: a very small person; specifically: a person of unusually small size who is physically well-proportioned. '' )〕 (''see Terminology''). Another definition for midget is any thing (especially an animal) that is small in proportion to a typical specimen. Hypotonia, or low muscle tone, is common in dwarfs, but intelligence and lifespan are usually normal. Defining dwarfism by height alone is problematic because short stature in itself is not a disorder. For example, pygmies have adult male heights of less than 150 cm (4 feet 11 inches) on average.〔(Encyclopædia Britannica - Pygmy ), retrieved on 2013-04-25〕 ==Classification== In men and women, the sole requirement for being considered a little person is having an adult height under 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: * location * * rhizomelic = root, e.g., bones of the upper arm or thigh * * mesomelic = middle, e.g., bones of the forearm or lower leg * * acromelic = end, e.g., bones of hands and feet. * * micromelic = entire limbs are shortened * source * * chondro = of cartilage * * osteo = of bone * * spondylo = of the vertebrae * * plasia = form * * trophy = growth Examples include achondroplasia, osseous dysplasia, chondrodystrophy, and osteochondrodystrophy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dwarfism」の詳細全文を読む スポンサード リンク
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