Dwarfism refers to a condition in individual plants or animals characterized by extreme small size. In older popular and medical usage, any type of marked human smallness could also be termed dwarfism. The term as related to human beings (the major subject of this article) is often used to refer specifically to those forms of extreme shortness characterized by disproportion of body parts, typically due to an inheritable disorder in bone or cartilage development.
Forms of extreme shortness in humans characterized by proportional body parts usually have a hormonal or nutritional cause. An example is growth hormone deficiency, once known as "pituitary dwarfism".
The Little People of America (LPA) defines dwarfism as a medical or genetic condition that usually results in an adult height of 4'10" (147 cm) or shorter.
Types:
* rhizomelic = root, e.g. bones of upper arm or thigh.
* mesomelic = middle, e.g. bones of forearm or lower leg.
* acromelic = end, e.g. bones of hands and feet.
When the cause of dwarfism is understood, it may be classified according to one of hundreds of names, which are usually permutations of the following roots:
* chondro = of cartilage.
* osteo = of bone.
* spondylo = of the vertebrae.
* plasia = form.
* trophy = growth.
Examples include achondroplasia, osseous dysplasia, chondrodystrophy, and osteochondrodystrophy.
The most recognizable and most common form of dwarfism is achondroplasia, which produces rhizomelic short limbs, increased spinal curvature, and distortion of skull growth. It accounts for 70% of dwarfism cases. Other relatively common types include spondyloepiphyseal dysplasia congenita (SED), diastrophic dysplasia, pseudoachondroplasia, hypochondroplasia, and osteogenesis imperfecta (OI). Severe shortness with skeletal distortion also occurs in several of the mucopolysaccharidoses and other storage diseases.
The average adult height of male and females with dwarfism is 132 cm and 123 cm respectively. The average weight of an adult may range from 100 to 150 pounds (45-68 kg).
Causes:
Most dwarfism-related conditions are genetic disorders, but the causes of some disorders are unknown. Most occurrences of dwarfism result from a random genetic mutation in either the father's sperm or the mother's egg — rather than being in one of the parent's complete genetic makeup.
Achondroplasia
For example, about 80 percent of people with achondroplasia are born to parents of average height. A person with achondroplasia and with two average-size parents received one mutated copy of the gene associated with the disorder and one normal copy of the gene. A person with the disorder may pass along either a mutated or normal copy to his or her own children.
Turner syndrome
Turner syndrome occurs because of a random deletion or severe alteration of an X chromosome, either in the sperm or egg. (The X chromosome is one of two chromosomes that determine the sex of a person. A female inherits an X chromosome from each parent, and a male inherits a Y chromosome from his father and an X chromosome from his mother.) A girl with Turner syndrome has only one fully functioning copy of the female sex chromosome rather than two.
Growth hormone deficiency
The cause of growth hormone deficiency can sometimes be traced to a genetic mutation or injury, but for most people with the disorder, no cause can be identified.
Other causes of dwarfism include deficiencies in other hormones and poor nutrition.
Symptoms:
More than 200 different medical conditions cause dwarfism. Therefore, dwarfism symptoms — other than short stature — vary considerably across the spectrum of disorders. In general, the disorders are divided into two broad categories.
Disproportionate dwarfism- If body size is disproportionate, some parts of the body are small and others are of average size or above-average size. Disorders causing disproportionate dwarfism inhibit the development of bones.
Proportionate dwarfism- A body is proportionately small if all parts of the body are small to the same degree and appear to be proportioned like a body of average stature.
Disproportionate dwarfism
Most people with dwarfism have disorders that cause disproportionately short stature. Usually, this means that a person has an average-size trunk and very short limbs, but some people may have a very short trunk and shortened (but disproportionately large) limbs. The other common characteristic of these disorders is the head being disproportionately larger than the body.
Almost all people with disproportionate dwarfism have normal intellectual capacities. Rare exceptions are usually the result of a secondary factor, such as excess fluid in the brain (hydrocephalus).
About 70 percent of all people with dwarfism have a disorder called achondroplasia, which causes disproportionately short stature. This disorder usually results in:
* An adult height of approximately 4 feet.
* An average-size trunk.
* Short arms and legs, with particularly short upper arms and legs.
* Short fingers, often with a wide separation between the middle and ring fingers.
* Limited mobility at the elbows.
* A disproportionately large head, with a prominent forehead and flattened bridge of the nose.
* Progressive development of bowed legs (genu varum).
* Progressive development of swayed lower back (lordosis).
A disorder called spondyloepiphyseal dysplasia congenita (SEDC), while rare, is the most common cause of disproportionate dwarfism with a short trunk. Signs and symptoms may include:
* Adult height ranging from 3 feet to just over 4 feet.
* A very short trunk, which may or may not be apparent in infancy.
* A short neck.
* Shortened arms and legs.
* Average-size hands and feet.
* Slightly flattened cheek bones.
* Hip deformities that result in thigh bones turning inward (coxa vara).
* Feet twisted or out of shape (clubfoot).
* Progressive hunching curvature of the upper spine (kyphoscoliosis).
* Progressive development of lordosis.
* Vision and hearing problems.
Proportionate dwarfism
Proportionate dwarfism results from medical conditions present at birth or during early childhood that limit overall growth and development. Therefore, the head, trunk and limbs are all small but of average proportions relative to each other.
Most of these disorders are uncommon, and signs and symptoms of the disorders vary greatly. Because these disorders affect overall growth, many of them result in poor development of one or more body systems. A few disorders causing proportionate dwarfism result in mental retardation.
Growth hormone deficiency is a relatively common cause of proportionate dwarfism. It occurs when the pituitary gland fails to produce an adequate supply of growth hormone, which is essential for regular childhood growth. Signs and symptoms include:
* Height below the fifth percentile on standard pediatric growth charts.
* Slowed growth before age 5.
* Periods of little or no change in height.
* Adult height usually less than 5 feet.
* Delayed or no sexual development during adolescence.
Turner syndrome, also relatively common, is a disorder that results in short stature and impaired sexual maturation in females. Signs and symptoms of the disorder may include:
* An average adult height of 4 feet 8 inches.
* Undeveloped ovaries.
* Excess skin at the neck at birth that usually becomes less noticeable over time.
* Puffy hands and feet at birth and during infancy.
* Heart and blood vessel defects.
* Kidney problems.
* No development of breasts or onset of menstruation during adolescence.
* Infertility.
* Possible difficulty with intellectual tasks dependent on visualizing objects in relation to one another.
Diagnosis:
Your pediatrician will examine a number of factors in order to assess your child's growth and determine if he or she has a dwarfism-related disorder. For some assessments, your pediatrician may refer you to other doctors, such as pediatricians specializing in bone abnormalities (orthopedics) or hormone dysfunction (endocrinology).
Measurements- A regular part of a well-baby medical examination is the measurement of height, weight and head circumference. At each visit, your pediatrician will plot these measurements on a chart, which indicates the percentile ranking for each measurement and expected growth curve in the future. This information is important for identifying abnormal growth, such as delayed growth or a disproportionately large head. If any trends in these charts are a concern, your pediatrician may make more frequent measurements over a period of several months.
Appearance- Many distinct facial and skeletal features are associated with each of several dwarfism disorders. Therefore, your child's appearance may also assist your pediatrician in making a diagnosis.
Imaging technology- Your doctor may order radiographic studies, such as X-rays, because certain abnormalities of the skull and skeleton can indicate which disorder your child may have. Various imaging devices may also reveal delayed maturation of bones, as is the case in growth hormone deficiency. A magnetic resonance imaging (MRI) scan may reveal abnormalities of the pituitary gland or hypothalamus, both of which play a role in hormone function.
Genetic tests- Genetic tests are available for many of the known causal genes of dwarfism-related disorders, but these tests often aren't necessary to make an accurate diagnosis. Your doctor is likely to suggest a test only to distinguish among possible diagnoses when other evidence is unclear or as a part of further family planning. If your pediatrician believes your daughter may have Turner syndrome, then he or she will order special laboratory tests that assess the state of X chromosomes extracted from blood cells.
Family history- Your pediatrician may take a history of stature in siblings, parents, grandparents or other relatives to help determine whether the average range of height in your family includes short stature.
Hormone tests- Your doctor may order tests that assess levels of growth hormone or other hormones that are critical for childhood growth and development.
Treatment:
Most dwarfism treatments don't increase stature but may alleviate problems caused by complications.
Common surgical treatments
Surgical procedures that may correct problems with bones in people with disproportionate dwarfism include:
* Inserting metal staples into the ends of long bones where growth occurs (growth plates) in order to correct the direction in which bones are growing.
* Dividing a limb bone, straightening it and inserting metal plates to hold it in place.
* Inserting rods or staples to help correct the shape of the spine.
* Increasing the size of the opening in bones of the spine (vertebrae) to alleviate pressure on the spinal cord.
Limb lengthening
Some people with dwarfism elect to undergo limb-lengthening surgery. With this procedure, the surgeon divides a long bone into two or more sections, separates the sections slightly and braces the bone and limb with metal "scaffolding." Pins and screws on this frame are adjusted to keep tension between the sections, enabling the bone to grow back together gradually into a complete but longer bone.
This procedure is controversial for many people with dwarfism because, as with all surgeries, there are risks, and because the "correction" in stature may imply there's something wrong with being short.
Hormone therapy
Growth hormone deficiency is treated with injections of a synthetic version of the hormone. Most children receive daily injections for several years until they reach a maximum adult height — often within the average adult range for one's family. Treatment may continue throughout adolescence and early adulthood to ensure adult maturation, such as appropriate gain in muscle or fat. The treatment may be supplemented with other related hormones if they are also deficient.
Treatment for Turner syndrome usually begins in the preteen years with small doses of a male hormone (androgen) and a female hormone (estrogen) to increase height. A second course of treatment with estrogen and another female hormone (progesterone) will occur in the early teen years to promote breast development and sexual maturation. Adult women usually use a hormone therapy until the average age for the onset of menopause.
Forms of extreme shortness in humans characterized by proportional body parts usually have a hormonal or nutritional cause. An example is growth hormone deficiency, once known as "pituitary dwarfism".
The Little People of America (LPA) defines dwarfism as a medical or genetic condition that usually results in an adult height of 4'10" (147 cm) or shorter.
Types:
* rhizomelic = root, e.g. bones of upper arm or thigh.
* mesomelic = middle, e.g. bones of forearm or lower leg.
* acromelic = end, e.g. bones of hands and feet.
When the cause of dwarfism is understood, it may be classified according to one of hundreds of names, which are usually permutations of the following roots:
* chondro = of cartilage.
* osteo = of bone.
* spondylo = of the vertebrae.
* plasia = form.
* trophy = growth.
Examples include achondroplasia, osseous dysplasia, chondrodystrophy, and osteochondrodystrophy.
The most recognizable and most common form of dwarfism is achondroplasia, which produces rhizomelic short limbs, increased spinal curvature, and distortion of skull growth. It accounts for 70% of dwarfism cases. Other relatively common types include spondyloepiphyseal dysplasia congenita (SED), diastrophic dysplasia, pseudoachondroplasia, hypochondroplasia, and osteogenesis imperfecta (OI). Severe shortness with skeletal distortion also occurs in several of the mucopolysaccharidoses and other storage diseases.
The average adult height of male and females with dwarfism is 132 cm and 123 cm respectively. The average weight of an adult may range from 100 to 150 pounds (45-68 kg).
Causes:
Most dwarfism-related conditions are genetic disorders, but the causes of some disorders are unknown. Most occurrences of dwarfism result from a random genetic mutation in either the father's sperm or the mother's egg — rather than being in one of the parent's complete genetic makeup.
Achondroplasia
For example, about 80 percent of people with achondroplasia are born to parents of average height. A person with achondroplasia and with two average-size parents received one mutated copy of the gene associated with the disorder and one normal copy of the gene. A person with the disorder may pass along either a mutated or normal copy to his or her own children.
Turner syndrome
Turner syndrome occurs because of a random deletion or severe alteration of an X chromosome, either in the sperm or egg. (The X chromosome is one of two chromosomes that determine the sex of a person. A female inherits an X chromosome from each parent, and a male inherits a Y chromosome from his father and an X chromosome from his mother.) A girl with Turner syndrome has only one fully functioning copy of the female sex chromosome rather than two.
Growth hormone deficiency
The cause of growth hormone deficiency can sometimes be traced to a genetic mutation or injury, but for most people with the disorder, no cause can be identified.
Other causes of dwarfism include deficiencies in other hormones and poor nutrition.
Symptoms:
More than 200 different medical conditions cause dwarfism. Therefore, dwarfism symptoms — other than short stature — vary considerably across the spectrum of disorders. In general, the disorders are divided into two broad categories.
Disproportionate dwarfism- If body size is disproportionate, some parts of the body are small and others are of average size or above-average size. Disorders causing disproportionate dwarfism inhibit the development of bones.
Proportionate dwarfism- A body is proportionately small if all parts of the body are small to the same degree and appear to be proportioned like a body of average stature.
Disproportionate dwarfism
Most people with dwarfism have disorders that cause disproportionately short stature. Usually, this means that a person has an average-size trunk and very short limbs, but some people may have a very short trunk and shortened (but disproportionately large) limbs. The other common characteristic of these disorders is the head being disproportionately larger than the body.
Almost all people with disproportionate dwarfism have normal intellectual capacities. Rare exceptions are usually the result of a secondary factor, such as excess fluid in the brain (hydrocephalus).
About 70 percent of all people with dwarfism have a disorder called achondroplasia, which causes disproportionately short stature. This disorder usually results in:
* An adult height of approximately 4 feet.
* An average-size trunk.
* Short arms and legs, with particularly short upper arms and legs.
* Short fingers, often with a wide separation between the middle and ring fingers.
* Limited mobility at the elbows.
* A disproportionately large head, with a prominent forehead and flattened bridge of the nose.
* Progressive development of bowed legs (genu varum).
* Progressive development of swayed lower back (lordosis).
A disorder called spondyloepiphyseal dysplasia congenita (SEDC), while rare, is the most common cause of disproportionate dwarfism with a short trunk. Signs and symptoms may include:
* Adult height ranging from 3 feet to just over 4 feet.
* A very short trunk, which may or may not be apparent in infancy.
* A short neck.
* Shortened arms and legs.
* Average-size hands and feet.
* Slightly flattened cheek bones.
* Hip deformities that result in thigh bones turning inward (coxa vara).
* Feet twisted or out of shape (clubfoot).
* Progressive hunching curvature of the upper spine (kyphoscoliosis).
* Progressive development of lordosis.
* Vision and hearing problems.
Proportionate dwarfism
Proportionate dwarfism results from medical conditions present at birth or during early childhood that limit overall growth and development. Therefore, the head, trunk and limbs are all small but of average proportions relative to each other.
Most of these disorders are uncommon, and signs and symptoms of the disorders vary greatly. Because these disorders affect overall growth, many of them result in poor development of one or more body systems. A few disorders causing proportionate dwarfism result in mental retardation.
Growth hormone deficiency is a relatively common cause of proportionate dwarfism. It occurs when the pituitary gland fails to produce an adequate supply of growth hormone, which is essential for regular childhood growth. Signs and symptoms include:
* Height below the fifth percentile on standard pediatric growth charts.
* Slowed growth before age 5.
* Periods of little or no change in height.
* Adult height usually less than 5 feet.
* Delayed or no sexual development during adolescence.
Turner syndrome, also relatively common, is a disorder that results in short stature and impaired sexual maturation in females. Signs and symptoms of the disorder may include:
* An average adult height of 4 feet 8 inches.
* Undeveloped ovaries.
* Excess skin at the neck at birth that usually becomes less noticeable over time.
* Puffy hands and feet at birth and during infancy.
* Heart and blood vessel defects.
* Kidney problems.
* No development of breasts or onset of menstruation during adolescence.
* Infertility.
* Possible difficulty with intellectual tasks dependent on visualizing objects in relation to one another.
Diagnosis:
Your pediatrician will examine a number of factors in order to assess your child's growth and determine if he or she has a dwarfism-related disorder. For some assessments, your pediatrician may refer you to other doctors, such as pediatricians specializing in bone abnormalities (orthopedics) or hormone dysfunction (endocrinology).
Measurements- A regular part of a well-baby medical examination is the measurement of height, weight and head circumference. At each visit, your pediatrician will plot these measurements on a chart, which indicates the percentile ranking for each measurement and expected growth curve in the future. This information is important for identifying abnormal growth, such as delayed growth or a disproportionately large head. If any trends in these charts are a concern, your pediatrician may make more frequent measurements over a period of several months.
Appearance- Many distinct facial and skeletal features are associated with each of several dwarfism disorders. Therefore, your child's appearance may also assist your pediatrician in making a diagnosis.
Imaging technology- Your doctor may order radiographic studies, such as X-rays, because certain abnormalities of the skull and skeleton can indicate which disorder your child may have. Various imaging devices may also reveal delayed maturation of bones, as is the case in growth hormone deficiency. A magnetic resonance imaging (MRI) scan may reveal abnormalities of the pituitary gland or hypothalamus, both of which play a role in hormone function.
Genetic tests- Genetic tests are available for many of the known causal genes of dwarfism-related disorders, but these tests often aren't necessary to make an accurate diagnosis. Your doctor is likely to suggest a test only to distinguish among possible diagnoses when other evidence is unclear or as a part of further family planning. If your pediatrician believes your daughter may have Turner syndrome, then he or she will order special laboratory tests that assess the state of X chromosomes extracted from blood cells.
Family history- Your pediatrician may take a history of stature in siblings, parents, grandparents or other relatives to help determine whether the average range of height in your family includes short stature.
Hormone tests- Your doctor may order tests that assess levels of growth hormone or other hormones that are critical for childhood growth and development.
Treatment:
Most dwarfism treatments don't increase stature but may alleviate problems caused by complications.
Common surgical treatments
Surgical procedures that may correct problems with bones in people with disproportionate dwarfism include:
* Inserting metal staples into the ends of long bones where growth occurs (growth plates) in order to correct the direction in which bones are growing.
* Dividing a limb bone, straightening it and inserting metal plates to hold it in place.
* Inserting rods or staples to help correct the shape of the spine.
* Increasing the size of the opening in bones of the spine (vertebrae) to alleviate pressure on the spinal cord.
Limb lengthening
Some people with dwarfism elect to undergo limb-lengthening surgery. With this procedure, the surgeon divides a long bone into two or more sections, separates the sections slightly and braces the bone and limb with metal "scaffolding." Pins and screws on this frame are adjusted to keep tension between the sections, enabling the bone to grow back together gradually into a complete but longer bone.
This procedure is controversial for many people with dwarfism because, as with all surgeries, there are risks, and because the "correction" in stature may imply there's something wrong with being short.
Hormone therapy
Growth hormone deficiency is treated with injections of a synthetic version of the hormone. Most children receive daily injections for several years until they reach a maximum adult height — often within the average adult range for one's family. Treatment may continue throughout adolescence and early adulthood to ensure adult maturation, such as appropriate gain in muscle or fat. The treatment may be supplemented with other related hormones if they are also deficient.
Treatment for Turner syndrome usually begins in the preteen years with small doses of a male hormone (androgen) and a female hormone (estrogen) to increase height. A second course of treatment with estrogen and another female hormone (progesterone) will occur in the early teen years to promote breast development and sexual maturation. Adult women usually use a hormone therapy until the average age for the onset of menopause.
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