How is dwarfism passed on

There is nothing a parent could do before or during pregnancy to prevent this change from happening. A genetic counselor can help determine the chances of having a child with dwarfism. Depending on the type of dwarfism, two average-height parents can have a child with short stature. It's also possible for two parents with dwarfism to have an average-height child. Individuals with dwarfism all have short stature. But there are many different causes of dwarfism. Each has their own unique features and physical traits.

In general, dwarfism caused by a skeletal dysplasia results in disproportionate short stature. This means that the limbs arms and legs and the trunk are not of the same proportion as average-height individuals. By far the most common skeletal dysplasia is achondroplasia. This short-limb dwarfism happens in about 1 of every 25, babies born of all races and ethnic groups. People with achondroplasia have a relatively long trunk and shortened arms and legs.

This is most noticeable in the upper parts of their arms and legs called rhizomelic shortening. Diastrophic dysplasia is another short-limb dwarfism. It happens in about 1 in , births. People who have this type tend to have shortened forearms and calves called mesomelic shortening. They might also have:. Most people with diastrophic dysplasia have joint changes that limit movement. People with diastrophic dysplasia often benefit from mobility aids , such as crutches, a scooter, or a wheelchair to get around.

Spondyloepiphyseal dysplasias SED are short-trunk skeletal dysplasias that involve the spine and the end of the bones that make up the joints epiphyses. Along with achondroplasia and diastrophic dysplasia, they're one of the more common types of dwarfism. In one type of SED, the short trunk may not be noticed until the child is school age.

Other types are seen at birth. People who have achondroplasia have abnormal bone growth that causes the following clinical symptoms: short stature with disproportionately short arms and legs, short fingers, a large head macrocephaly and specific facial features with a prominent forehead frontal bossing and mid-face hypoplasia. Infants born with achondroplasia typically have weak muscle tone hypotonia.

Because of the hypotonia, there may be delays in walking and other motor skills. People with achondroplasia commonly have breathing problems in which breathing stops or slows down for short periods apnea.

Other health issues include obesity and recurrent ear infections. Adults with achondroplasia may develop a pronounced and permanent sway of the lower back lordosis and bowed legs. The problems with the lower back can cause back pain leading to difficulty with walking.

Achondroplasia is diagnosed by characteristic clinical and X-ray findings in most affected individuals. In individuals who may be too young to make a diagnosis with certainty or in individuals who do not have the typical symptoms, genetic testing can be used to identify a mutation in the FGFR3 gene.

Genetic testing can identify mutations in 99 percent of individuals who have achondroplasia. 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. 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.

Researchers believe there are more than conditions that cause dwarfism. 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. 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. The pregnancy may go to full term, but the baby is usually much smaller than average.

The result is typically proportional dwarfism. 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.

Individuals who inherit two altered copies of this gene typically have a severe form of achondroplasia that causes extreme shortening of the bones and an underdeveloped rib cage. These individuals are usually stillborn or die shortly after birth from respiratory failure. Genetics Home Reference has merged with MedlinePlus. Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.

From Genetics Home Reference. Description Achondroplasia is a form of short-limbed dwarfism. Frequency Achondroplasia is the most common type of short-limbed dwarfism. Inheritance Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Research Studies from ClinicalTrials. Fibroblast growth factor receptor 3 mutations in achondroplasia and related forms of dwarfism.