Skeletal Dysplasia (Dwarfism) and Other Causes of Short Stature
What does “short stature” mean?
“Short stature” is a term that refers to when a person is significantly shorter than other people the same age and sex. In children this can mean that their height is low on growth curves, or less than expected based on their parents’ heights.
A person’s standing height (or length in babies) is determined by a number of factors including how tall the parents are, their weight and hormone levels. There are also a number of genetic conditions that can cause people to be short.
What is skeletal dysplasia (dwarfism)?
One set of genetic conditions that can cause short stature is called skeletal dysplasia.
Skeletal dysplasia is an umbrella medical term that includes hundreds of conditions that can affect the growth of bone and/or cartilage. In the past these conditions were referred to as “dwarfism.” Some people who have these conditions prefer the term “little people,” usually adults less than 4 foot 10 inches.
Skeletal dysplasia has many different forms. These conditions can affect different parts of the body including the size of arms, legs, abdomen and or head. Because of this they can also be described as being of “disproportionate” short stature.
Symptoms and Causes
What is the most common cause of skeletal dysplasia (dwarfism)?
There are hundreds of genetic conditions known to cause skeletal dysplasia. The most common is achondroplasia, a birth defect that affects bone growth and causes arms and legs to be short. People with achondroplasia have an average adult height of about 4 feet.
Achondroplasia can be inherited from a parent, but most cases are the result of a new genetic mutation, meaning neither parent has passed it on. It’s common for people with achondroplasia to have a large head with a prominent forehead, bowed legs and a curvature of the back that is called “lordosis.”
Achondroplasia usually does not affect a person’s intelligence or lifespan, although potential complications can be associated with it.
What are other causes of skeletal dysplasia (dwarfism)?
- Hypochondroplasia is another condition that affects bone growth, usually with less severe effects that might not be noticed during infancy.
- Pseudoachondroplasia is yet another condition that affects bone growth. Like achondroplasia and hypochondroplasia, it limits the body’s ability to turn cartilage into bone.
- Diastrophic dysplasia is another condition that can cause short-limbed dwarfism. Distinguishing features of diastrophic dysplasia can include deformities of the feet and thumbs and pain in the joints. Some infants affected by diastrophic dysplasia have a cleft palate, an opening in the roof of the mouth.
- Spondyloepiphyseal dysplasia congenita has a name that refers to the spine (spondylo-) and the ends (epiphyses) of long bones in the arms and legs. It is sometimes abbreviated as SEDc. A short trunk and neck and curvature of the spine are typical of people with SEDc, as well as vision and hearing problems.
What are other causes of short stature?
Most other causes of being short are described as “proportionate,” meaning that everything is small and not just certain parts such as the arms or legs.
- Familial: If parents and other family members are short than it can be normal for the child to be short.
- Late bloomer (constitutional delay): Some children are short earlier in childhood because they are programmed to grow later than their peers. There is sometimes a family history of a similar pattern of growth in other members.
- Malnutrition: Not having adequate nutrition (for a wide array of reasons) can affect a child’s ability to grow.
- Growth hormone deficiency: The brain doesn’t make enough of the hormone that causes most of a child’s growth. The deficiency can be treated with injections.
- Small for gestational age: Most babies that are born small will “catch up” with their growth within the first 2-3 years of life, but 10% do not. Those that remain small may benefit from treatment with growth hormone.
- Genetic conditions: A large number of other genetic conditions can result in individuals being shorter than expected.
Diagnosis and Tests
How is skeletal dysplasia (dwarfism) diagnosed?
Many of these conditions can sometimes be diagnosed, or at least suspected, before birth. An ultrasound image – a standard part of pre-natal screening – can alert your doctor to signs such as shortened bones.
After birth, your pediatrician will keep track of your child’s growth and make observations about the child’s appearance. Testing, including blood work and X-rays, can shed light on reasons why the child is shorter than expected, and whether or not there is concern for a possible skeletal dysplasia. You may also need to meet with specialists such as pediatric endocrinologists (hormone doctors) or geneticists.
What is the risk of having a child with achondroplasia?
Achondroplasia affects somewhere between 1 in 15,000 and 1 in 40,000 children. In most cases the mutation happens on its (own) and is not passed on from parents. The chance increases drastically if one or both parents has achondroplasia. A parent with achondroplasia has a 50 percent chance of passing the condition on to a child. If both parents have achondroplasia there is a 25 percent chance the child will be born with what is called homozygous achondroplasia, which leads to stillbirth or death shortly after birth.
Management and Treatment
How is skeletal dysplasia (dwarfism) treated?
In general, management of is focused on dealing with the symptoms and complications. There is no cure. For example, complications that can come with achondroplasia, the most common cause of skeletal dysplasia, include:
- Hydrocephalus, excess water around the brain, which might in some cases have to be drained.
- Compression of the brain stem, the part of the brain that connects to the spinal cord. If the opening at the base of the skull is too small, it can cause breathing problems. This can be treated with surgery to enlarge the opening.
- Apnea, which is the term for a temporary lapse in breathing, often during sleep. This can be treated in various ways including machines to help the child breathe, medications and surgery to open up the airway by removing the tonsils and adenoids.
- Greater susceptibility to ear infections, which can be treated with antibiotics or ear tubes that allow air into the ear and prevent the buildup of fluid.
- An increased risk of obesity, which is best addressed by encouraging healthy eating habits and exercise from early childhood onward.
Some people who have skeletal dysplasia choose to have limb lengthening surgery, which involves cutting the bone and implanting metal devices in it. This option is controversial because it’s a complicated procedure with a limited record of success and substantial risk of complications. Some see it, too, as a purely cosmetic procedure that doesn’t address any actual health problems.
Outlook / Prognosis
What is the outlook for people with short stature and skeletal dysplasia (dwarfism)?
Most people of short stature have normal intelligence, a normal life span, and what the organization Little People of America characterizes as “reasonably good health.” But the various complications that can result from various causes of dwarfism do take a toll. Orthopedic complications often require surgery.
How can I help my child who is short stature?
Self-esteem is important for all children. Children might be teased or bullied at school or face other pressures related to the value society places on height. It’s a good idea to talk to teachers to educate them about your child needs.
Parents need to balance the need to treat a child in a manner appropriate for his or her age, not his or her stature, with concern for difficulties and safety issues that range from obvious to not-so-obvious. (For example, a child with short-limbed dwarfism might have a higher center of gravity that requires a different way of securing them in a swing or a stroller.)
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