Dwarfism is short stature that results from a genetic or medical condition. Dwarfism is generally defined as an adult height of 4 feet 10 inches (147 centimeters) or less. The average adult height among people with dwarfism is 4 feet (122 cm).
Many different medical conditions cause dwarfism. In general, these disorders are categorized 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. Medical conditions present at birth or appearing in early childhood limit overall growth and development.
Some people prefer the term “short stature” or “little people” rather than “dwarf” or “dwarfism.”It is so important to be sensitive to the preference of someone who has this disorder. Short stature disorders do not include familial short stature — a short height that’s considered a normal variation with normal bone development.
Types of dwarfism
Though there are many different causes of dwarfism, there are two main types of the condition: proportionate and disproportionate.
When the head, trunk, and limbs are all proportionate to each other, but much smaller than those of an average-sized person, the condition is known as proportionate dwarfism.
This type of dwarfism is often the result of a hormone deficiency. It can often be treated with hormone injections while a child is still growing. As a result, someone born with proportionate dwarfism may be able to reach an average height or get close to it.
This is the most common kind of dwarfism. As the name suggests, it’s characterized by having body parts that are disproportionate to each other. For example, a genetic condition called achondroplasia results in arms and legs that are significantly shorter than those of a person of average size, but the trunk is like that of someone unaffected by dwarfism. In some cases, the head of a person with disproportionate dwarfism may be slightly larger than that of a person without dwarfism.
Signs and symptoms — other than short stature — vary considerably across the spectrum of disorders.
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. In these disorders, the head is disproportionately large compared with 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 around the brain (hydrocephalus).
The most common cause of dwarfism is a disorder called achondroplasia, which causes disproportionately short stature. This disorder usually results in the following:
- An average-size trunk
- Short arms and legs, with particularly short upper arms and upper 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 a flattened bridge of the nose
- Progressive development of bowed legs
- Progressive development of swayed lower back
- An adult height around 4 feet (122 cm)
Another cause of disproportionate dwarfism is a rare disorder called spondyloepiphyseal dysplasia congenita (SEDC). Signs may include:
- A very short trunk
- A short neck
- Shortened arms and legs
- Average-size hands and feet
- Broad, rounded chest
- Slightly flattened cheekbones
- Opening in the roof of the mouth (cleft palate)
- Hip deformities that result in thighbones turning inward
- A foot that’s twisted or out of shape
- Instability of the neck bones
- Progressive hunching curvature of the upper spine
- Progressive development of swayed lower back
- Vision and hearing problems
- Arthritis and problems with joint movement
- Adult height ranging from 3 feet (91 cm) to just over 4 feet (122 cm)
It’s a result of medical conditions present at birth or appearing in early childhood that limit overall growth and development. So the head, trunk, and limbs are all small, but they’re proportionate to each other. Because these disorders affect overall growth, many of them result in poor development of one or more body systems.
Growth hormone deficiency is a relatively common cause. It occurs when the pituitary gland fails to produce an adequate supply of growth hormone, which is essential for normal childhood growth. Signs include:
- Height below the third percentile on standard pediatric growth charts
- Growth rate slower than expected for age
- Delayed or no sexual development during the teen years
Researchers believe there are more than 300 conditions that cause it. Most causes are genetic. The most common causes include:
Though achondroplasia is a genetic condition, four out of five people who have it also have two parents who are average-sized. If you have achondroplasia, you have one mutated gene associated with the condition and one unaffected version of that gene. This is the most common cause of dwarfism.
This condition affects only females. Instead of inheriting two fully functioning X chromosomes from your parents, you inherit one X chromosome and are missing a second, or at least part of a second, X chromosome. Males, by comparison, have an X chromosome and a Y chromosome.
Growth hormone deficiency
The reasons for growth hormone deficiency aren’t always clear. And sometimes it’s tied to a genetic mutation. In many cases, the reasons for growth hormone deficiency are never diagnosed.
An underactive thyroid, especially if it develops at a young age, can lead to many health problems, including limited growth. Other complications include low energy, cognitive problems, and puffy facial features.
A newborn’s thyroid health should be checked as a matter of routine screenings. If your baby didn’t have their thyroid checked, discuss it with your pediatrician.
Intrauterine growth retardation
This condition develops while the baby is still in the mother’s womb. The pregnancy may go to full term, but the baby is usually much smaller than average. The result is typically proportional dwarfism.
Genetics and other risk factors
Dwarfism is usually the result of a genetic mutation. But having a gene or genes responsible for dwarfism can occur in a couple of ways.
In some cases, it can happen spontaneously. You may not be born with mutated genes inherited from a parent. Instead, a mutation of your genes happens on its own — usually without a cause doctors can discover.
Inherited genetic disorders can take two forms. One is recessive, which means you inherit two mutated genes (one from each parent) to have the condition. The other is dominant. You only need one mutated gene — from either parent — to have the disorder.
Other risk factors for dwarfism include hormone deficiency or malnutrition. Serious malnutrition, which leads to weak bones and muscles, can also be overcome in many cases with a healthier, and more nutrient-rich diet.
At birth, sometimes the appearance of a newborn may be enough to make a diagnosis. As part of baby wellness exams, your child should be measured and weighed to see how they compare to the population averages for a child their age. Consistently measuring in the lowest quartiles on the standard growth chart is another sign a pediatrician can use to diagnose dwarfism.
Making a tentative prenatal diagnosis while the baby is still in the womb can be done with an ultrasound. If the baby’s appearance suggests dwarfism, or if the parents know they carry a gene for dwarfism, a doctor may recommend amniocentesis. This is a lab test of amniotic fluid from the womb.
Genetic testing may be helpful in some cases. This is particularly true when distinguishing one potential cause of dwarfism from another. A blood test to check for growth hormone levels may also help confirm a diagnosis of dwarfism caused by hormone deficiency.
Complications of dwarfism-related disorders can vary greatly, but some complications are common to a number of conditions.
The characteristic features of the skull, spine, and limbs shared by most forms of disproportionate dwarfism result in some common problems:
- Delays in motor skills development, such as sitting up, crawling and walking
- Frequent ear infections and risk of hearing loss
- Bowing of the legs
- Difficulty breathing during sleep (sleep apnea)
- Pressure on the spinal cord at the base of the skull
- Excess fluid around the brain (hydrocephalus)
- Crowded teeth
- Progressive severe hunching or swaying of the back with back pain or problems breathing
- Narrowing of the channel in the lower spine (spinal stenosis), resulting in pressure on the spinal cord and subsequent pain or numbness in the legs
- Weight gain that can further complicate problems with joints and the spine and place pressure on nerves
With proportionate dwarfism, problems in growth and development often result in complications with poorly developed organs. For example, heart problems that often occur with Turner syndrome can have a significant effect on health. An absence of sexual maturation associated with growth hormone deficiency or Turner syndrome affects both physical development and social functioning.
Women with disproportionate dwarfism may develop respiratory problems during pregnancy. A C-section (cesarean delivery) is almost always necessary because the size and shape of the pelvis don’t allow for successful vaginal delivery.
They don’t want to label, as people with conditions. However, some people may refer to themselves as dwarfs, little people or people of short stature. Calling them “midget” is already considered offensive.
People of average height may have misconceptions about people with dwarfism. And the portrayal of people with dwarfism in modern movies often includes stereotypes. Misconceptions can impact a person’s self-esteem and limit opportunities for success in school or employment.
Children with dwarfism are particularly vulnerable to teasing and ridicule from classmates. Because dwarfism is relatively uncommon, children may feel isolated from their peers.