Why is dwarfism caused

People with dwarfism have short stature. This means that their height is under 4' 10" as an adult. They are usually of normal intelligence. Dwarfism most often does happen in families where both parents are of average height. More than different conditions can cause dwarfism.

Achondroplasia is the most common type of dwarfism. Achondroplasia is a genetic condition that affects about 1 in 15, to 1 in 40, people. 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. But society might consider a person to be a dwarf based on short stature alone. Dwarfism has many different causes. Several of the causes of dwarfism can lead to other health problems, such as osteoarthritis. Some conditions that cause dwarfism disrupt the hormones that enable the body to grow. Dwarfism can also be due to metabolic disorders or malnourishment. A group of conditions called skeletal dysplasias is the most common cause of dwarfism.

Skeletal dysplasias cause the bones to grow abnormally, resulting in a small stature. This abnormal growth can also result in uneven growth that produces a body of unusual proportions. Typically, skeletal dysplasias are genetic conditions.

Most people with skeletal dysplasias have parents of normal stature. The three most common types of skeletal dysplasias are achondroplasia, spondyloepiphyseal dysplasia congenita, and diastrophic dysplasia. Early in childhood, much of the cartilage a person is born with transforms into harder bone. In achondroplasia, this process does not happen as effectively. Achondroplasia primarily affects the bones of the arms and legs.

Achondroplasia is a genetic disorder present at birth. Its symptoms include:. Some people with achondroplasia develop bone issues, such as scoliosis , have difficulty breathing, or suffer from a narrowing of the spine called spinal stenosis.

A rare form of achondroplasia occurs when people inherit two copies of a mutated gene that causes achondroplasia. This leads to very short bones and a poorly-developed rib cage. Most people with this disorder are stillborn or die in infancy because they cannot breathe. Spondyloepiphyseal dysplasia congenita SEDc is a genetic mutation that causes a short torso, short arms, and short legs. Read more about treatments for restricted growth. Page last reviewed: 30 March Next review due: 30 March There are 2 main types of restricted growth: proportionate short stature PSS — a general lack of growth in the body, arms and legs disproportionate short stature DSS — where the arms and legs are particularly short As well as being short, some people with restricted growth also have other physical problems, such as bowed legs or an unusually curved spine.

What causes restricted growth? Causes of PSS The most common cause of PSS is being born to small parents, but it's sometimes the result of the body not producing enough growth hormone. It causes poor bone growth, resulting in short upper arms and thighs.