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.
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.