Despite misconceptions, dwarfism is not a disease or developmental disorder. Different organizations have different criteria for what dwarfism entails. For example, Little People of America is an advocacy group that defines dwarfism as any condition that causes a fully grown adult to have a height under 4 feet 10 inches. Many organizations and individuals, particularly in the medical community, prefer to use the term “short stature” rather than dwarfism. The clinical definition of short stature is a height within the lowest 2.3 percent of the general population.
Ultimately, there are hundreds of different conditions that cause short stature. Due to this, physicians categorize the occurrences based on whether the factors cause proportionate or disproportionate dwarfism. Proportionate dwarfism describes an individual whose body parts, while small, retain similar proportions to an average body. Hormone deficiencies are the most common cause of proportionate dwarfism. In such cases, hormone treatments can help infants or children grow to an average height in adulthood.
The more common form of dwarfism is disproportionate dwarfism. A person with disproportionate dwarfism may have some areas of the body that are below-average length or size, while other portions may be average or above-average. For example, a person’s arms and legs may be disproportionate to their head and body, in relation to the majority population. Conditions responsible for disproportionate dwarfism typically limit bone development. Because of this, people may require tools such as crutches or wheelchairs to improve mobility.
The most common cause of short stature, achondroplasia, accounts for around 70 percent of all cases. Physicians frequently discover this condition before a child’s birth using ultrasounds. As babies develop, their skeletal structures change as cartilage hardens into bone. Achondroplasia is a genetic condition that prevents the cartilage from properly becoming bone, potentially causing changes in development such as shorter limbs, skull distortion, and increased spinal curvature. Adults with achondroplasia may experience difficulty breathing as a result of their head placing pressure on their upper spinal cord.
Some conditions that cause short stature do not appear in fetuses or infants. For example, signs of pseudoachondroplasia are usually not visible until the child is between two or three years old. Starting at this age, the child may not experience the same rate of growth as their peers. Their lower limbs may develop abnormally, and their fingers may remain relatively short. Some physicians misdiagnose pseudoachondroplasia as achondroplasia or hypochondroplasia, but these conditions have distinct genetic origins.
Hypochondroplasia has a similar genetic basis to achondroplasia. The former, however, is usually not identifiable in fetuses or infants. Several characteristics frequently appear as a result of hypochondroplasia. As the child grows, their arms and legs do not properly develop. Their body may also be shorter than average. Additionally, the fingers and toes of a person with hypochondroplasia may not reach average length. Orthopedic surgeries and physical therapy may alleviate some of the issues caused by hypochondroplasia.
A rare disorder called spondyloepiphyseal dysplasia congenita dramatically affects bone growth, causing short stature, skeletal abnormalities, and potential visual or auditory problems. Physicians typically refer to this condition as SED or SDC. Typically, a child born with SED has a short torso, neck, and limbs while their hands and feet are of average size. SED affects many bones, placing people with the condition at risk of flattened vertebrae, spinal cord damage, and inward-turning leg bones.
Both children and adults may experience a deficiency of growth hormone. A person with a growth hormone deficiency will have slower muscular development and weaker bones. In children, a lack of growth hormone usually results in slow or stunted growth, potentially causing short stature. It may also delay puberty by several years. Physicians may administer daily injections of growth hormone through childhood to allow children with the condition to reach a more average height. Adults with the deficiency typically receive a weekly dose of this essential hormone.
Like many of the disproportionate dwarfism disorders, diastrophic dysplasia is a disorder of cartilage and bone development. Diastrophism refers to the Greek word meaning "twisting." This condition earned its name because it causes a rare twisting of the metatarsal bones in the feer, leading to clubfoot, where the feet turn inward and upward. Many people with diastrophic dysplasia also have "hitchhiker’s thumbs." Typically, individuals born with diastrophic dysplasia have short stature and short arms and legs. Joint problems that inhibit mobility are also common.
Humans have a total of 46 chromosomes that store important genetic material. X and Y chromosomes determine a person’s sex. The female sex possesses two X chromosomes, while males have one X and one Y. Turner syndrome is a genetic condition that only affects females, when a portion or the entirety of one of the X chromosomes is missing. This can lead to short stature as well as hearing and vision issues. Many people with Turner syndrome develop heart defects and diabetes.
Usually, physicians diagnose short stature by observing a child. The vast majority of the conditions that cause short stature begin during fetal development, though the symptoms are not always visible at this point. Before a child is born, ultrasounds may identify signs of one of these conditions. After birth, skeletal dysplasia conditions such as achondroplasia are relatively easy for doctors to diagnose because of the higher chance for characteristic physical changes. X-ray scans can confirm a diagnosis. Some conditions cause subtle short stature that doctors may have difficulty diagnosing or not immediately notice.
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