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What is Dwarfism?
According to the advocacy group Little People of America (LPA), dwarfism is a term that denotes short stature. For humans, dwarfism is defined as any adult with a height of 4 feet 10 inches or less. The most typical range in adult height among people with dwarfism is 2 feet 8 inches to 4 feet 8 inches.
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What Causes Dwarfism?
There are many causes of dwarfism. In fact, more than 200 conditions are known to cause short stature. However, one medical condition, achondroplasia, accounts for the majority of the cases of dwarfism.
Achondroplasia is the most common type of short-limbed dwarfism. Typical features of people with achondroplasia includes: average-size trunk, short arms and legs with particularly short upper arms and thighs, limited range of motion at the elbows, and an enlarged head (macrocephaly). The condition occurs in 1 in 15,000 to 40,000 newborns.
Genetic abnormalities (mutations) on a gene known as FGFR3 are the underlying cause of achondroplasia. The FGFR3 gene codes for a specific protein involved in the development and maintenance of bone and brain tissue. This protein limits the formation of bones from cartilage, interfering with skeletal development and bone growth.
Another important cause of dwarfism is the deficiency of a hormone known as Growth Hormone (GH) (somatotropin). In this case, insufficient amounts of GH may cause children to grow slowly or even indefinitely. There is no single cause for GH deficiency. It may be caused by a genetic disorder or damage to the pituitary gland. Even poor nutrition can cause GH deficiency.
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Are There Different Types of Dwarfism?
Yes. Since the only parameter for defining dwarfism is being shorter than 4 feet 10 then any condition that causes this may be defined as a type of dwarfism. A way to classify dwarfism is related to the underlying cause. For example achondroplasia is related to the malformation of cartilage, osseous dysplasia to the malformation of bones.
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Are There Treatments for Dwarfism?
Treatments are aimed at alleviating problems caused by dwarfism rather than increasing stature. In the case of GH deficiency, children may receive daily injections of the hormone until they reach the average family’s adult height. There are also some surgical procedures that some people with dwarfism elect to go for. For example, in limb lengthening limbs are placed with a metal "scaffolding." It's based on the principle that a section of bone that is cut during surgery and then pulled apart will encourage new bone growth.
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How Is Achondroplasia Inherited?
Achondroplasia has an autosomal dominant pattern of inheritance, which means that one copy of the altered gene is enough for an individual to inherit the condition. Eighty percent of people with achondroplasia have average-size parents, and so the mutation on the FGFR3 gene is new. The remaining 20% of people with achondroplasia receive an altered copy from one or two affected parents. If an individual inherits two forms of the altered gene, they are unlikely to live for more than a few days after birth. Many are still born.