What Is Dwarfism?
Dwarfism is when a person is short in stature because of their genes or a medical reason. It’s defined by the advocacy groups Little People of the World Organization (LPOTW) and Little People of America (LPA) as an adult height of 4 feet 10 inches or under, as a result of a medical or genetic condition. Other groups extend the criteria for certain forms of dwarfism to 5 feet, but the average height of an adult with dwarfism is 4 feet.
There are two main categories of dwarfism -- disproportionate and proportionate.
Disproportionate dwarfism is characterized by an average-size torso and shorter arms and legs or a shortened trunk with longer limbs.
In proportionate dwarfism, the body parts are in proportion but shortened.
In addition to short stature, dwarfism has many other symptoms that can vary depending the type it is.
Disproportionate dwarfism symptoms
Symptoms of disproportionate dwarfism may include:
- Adults typically are about 4 feet tall
- Average-size torso and very short limbs, especially in the upper halves of arms and legs
- Short fingers
- Wide spaces between the middle and ring fingers
- Limited elbow mobility
- Disproportionately large head
- Prominent forehead
- Flattened bridge of the nose
- Bowing of legs that progressively worsens over time
- Swaying of the back that progressively worsens over time
Some people with disproportionate dwarfism have a rare disorder called spondyloepiphyseal dysplasia congenita (SEDC). Adults with SEDC are around 3 to 4 feet tall and may have these signs too:
- Very short trunk
- Short neck, arms, and legs, but average-size hands and feet
- Broad chest
- Flattened cheekbones
- Cleft palate, or an opening in the roof of the mouth
- Unstable neck bones
- Deformed hips where the thigh bones turn inward
- Twisted feet
- Hunched upper back that progressively worsens
- Swayed lower back that progressively worsens
- Joint mobility problems
- Impaired vision or hearing
Proportionate dwarfism symptoms
Proportionate dwarfism is caused by a medical condition you have at birth or that develops in childhood that hinders growth and development. One common cause is too-low amounts of growth hormone produced by your pituitary gland.
Symptoms of proportionate dwarfism include a smaller head, arms, and legs. But all are in proportion with each other. Organ systems may be smaller too.
Other signs of proportionate dwarfism in children are:
- Slower growth rate than expected for their age
- Height lower than the third percentile on standard charts for age
- Delayed or no sexual development during the teen years
There are approximately 400 types of dwarfism. Causes of proportionate dwarfism include metabolic and hormonal disorders such as growth hormone deficiency.
The most common types of dwarfism, known as skeletal dysplasias, are genetic. Skeletal dysplasias are conditions of abnormal bone growth that cause disproportionate dwarfism.
Achondroplasia. The most common form of dwarfism -- accounting for 70% of cases -- achondroplasia occurs in about one out of 26,000 to 40,000 babies and is evident at birth. People with achondroplasia have a relatively long trunk and shortened upper parts of their arms and legs. Other features of achondroplasia include:
- A large head with a prominent forehead
- A flattened bridge of the nose
- Protruding jaw
- Crowded and misaligned teeth
- Forward curvature of the lower spine
- Bowed legs
- Flat, short, broad feet
Spondyloepiphyseal dysplasias (SED).A less common form of dwarfism, SED affects approximately one in 95,000 babies. Spondyloepiphyseal dysplasia refers to a group of conditions characterized by a shortened trunk, which may not become apparent until a child is between ages 5 and 10. Other features can include:
- Club feet
- Cleft palate
- Severe osteoarthritis in the hips
- Weak hands and feet
- Barrel-chested appearance
Diastrophic dysplasia.A rare form of dwarfism, diastrophic dysplasia occurs in about one in 100,000 births. People who have it tend to have shortened forearms and calves (this is known as mesomelic shortening).
Other signs can include
- Deformed hands and feet
- Limited range of motion
- Cleft palate
- Ears with a cauliflower appearance
Turner syndrome.This genetic condition only affects females. It’s caused by a missing or partial X chromosome. Girls with Turner syndrome only inherit one fully functioning X chromosome from their parents, instead of one from each parent.
Skeletal dysplasia is caused by a genetic mutation. The gene mutation can occur spontaneously or can be inherited.
Diastrophic dysplasia and usually spondyloepiphyseal dysplasias are inherited in a recessive manner. This means a child must receive two copies of the mutated gene -- one from the mother, one from the father -- to be affected.
Achondroplasia, on the other hand, is inherited in a dominant manner. That means a child needs only one copy of the mutated gene to have that form of skeletal dysplasia. There is a 25% chance that a child born to a couple in which both parents have achondroplasia will be of normal height. But there is also a 25% chance the child will inherit both dwarfism genes, a condition known as double-dominant syndrome. This is a fatal condition that usually results in miscarriage.
Often parents of children with achondroplasia do not carry the mutated gene themselves. The mutation in the child occurs spontaneously at the time of conception.
Doctors do not know what causes a gene to mutate. It is a seemingly random occurrence that can happen in any pregnancy. When average-size parents have a child with dwarfism due to a spontaneous mutation, it is not likely that other children will also have the mutation.
In addition to genetic skeletal dysplasia, short stature has other causes, including disorders of the pituitary, which influence growth and metabolism; kidney disease; and problems that affect the body's ability to absorb nutrients.
Some forms of dwarfism are evident in utero, at birth, or during infancy and can be diagnosed through X-rays and a physical exam. A diagnosis of achondroplasia, diastrophic dysplasia, or spondyloepiphyseal dysplasia can be confirmed through genetic testing. In some cases, prenatal testing is done if there is concern for specific conditions.
Sometimes dwarfism doesn't become evident until later in a child's life, when dwarfism signs lead parents to seek a diagnosis. Here are signs and symptoms to look for in children that indicate a potential for dwarfism:
- A larger head
- Late development of certain motor skills, such as sitting up or walking
- Breathing problems
- Curvature of the spine
- Bowed legs
- Joint stiffness and arthritis
- Lower back pain numbness in the legs
- Crowding of teeth
Doctors may also use these tests to help diagnose dwarfism:
Appearance. Children with possible dwarfism may have changes to their skeleton or facial structures as they develop.
Chart comparisons. At regular check-ups, your child’s height, weight, and head circumference will be measured and compared to percentiles for standard development for their age. If your child shows any signs of abnormal growth, they may need more frequent measurements.
Imaging.Doctors may spot signs of achondroplasia, such as shorter limbs, or other causes of dwarfism on ultrasounds of a fetus during pregnancy. X-rays of babies or children may show that their arms or legs are not growing at a normal rate, or that their skeleton shows signs of dysplasia. MRI scans can show any abnormalities of the pituitary gland or hypothalamus, which affect hormone production.
Genetic testing.DNA tests may be done before or after birth to look for genetic mutations linked to dwarfism. Girls with suspected Turner syndrome may need DNA tests to check their X chromosomes. DNA testing may help parents with family planning if they wish to have more children.
Family history.Pediatricians may check the height and size of other family members, such as siblings, to compare with the child with suspected dwarfism.
Hormone tests.Tests of growth hormone levels can confirm if they’re low.
Early diagnosis and treatment can help prevent or lessen some of the problems associated with dwarfism. People with dwarfism related to growth hormone deficiency can be treated with growth hormone. For children five years of age and older with achondroplasia who still have the potential for growth, the FDA has approved vosoritide (Voxzogo) to help stimulate bone growth.
In many cases, people with dwarfism have orthopaedic or medical complications. Treatment of those can include:
- Insertion of a shunt to drain excess fluid and relieve pressure on the brain
- A tracheotomy to improve breathing through small airways
- Corrective surgeries for deformities such as cleft palate, club foot, or bowed legs
- Surgery to remove tonsils or adenoids to improve breathing problems related to large tonsils, small facial structures, and/or a small chest
- Surgery to widen the spinal canal (the opening through which the spinal cord passes) to relieve spinal cord compression
- Extended limb lengthening, a controversial surgery, due in part to its risks, it involves several procedures. It is only done on adults.
Other treatment may include:
- Physical therapy to strengthen muscles and increase joint range of motion
- Back braces to improve curvature of the spine
- Placement of drainage tubes in the middle ear to help prevent hearing loss due to repeated ear infections
- Orthodontic treatment to relieve crowding of teeth caused by a small jaw
- Nutritional guidance and exercise to help prevent obesity, which can aggravate skeletal problems
Disproportionate dwarfism causes changes to the limbs, back, and head size that could cause complications like these:
- Back pain or breathing difficulties due to hunched or swayed back
- Bowed legs
- Crowded teeth
- Delayed motor skills development
- Frequent ear infections and possibly hearing loss
- Hydrocephalus (fluid on the brain)
- Pressure on the spine at the base of the skull
- Sleep apnea
- Spinal stenosis, a narrowing of the spine that may cause leg pain or numbness
- Weight gain that may cause back problems
Proportionate dwarfism may cause you to have smaller or less developed organs. Girls with Turner syndrome may have heart problems. Kids with lower growth hormone levels or Turner syndrome may have emotional or social problems due to delays in sexual development.
Women with disproportionate dwarfism may have pregnancy complications, such as respiratory problems. They almost always need to deliver their babies by C-section, as the shape of their pelvis makes vaginal delivery too difficult.
Anyone with dwarfism may encounter people who call them names or don’t understand their condition. Kids with dwarfism who have lower self-esteem may need emotional support from their parents to deal with their feelings.