The Most Common Types of Dwarfism

Causes of Short Stature

Pregnant woman having ultrasound scan

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Dwarfism means that a person has short stature due to a genetic or medical condition, with an adult height of 4 feet, 10 inches or less. There are an estimated 300 types of dwarfism. People with these conditions typically have normal intelligence and abilities, although some conditions can cause other health problems.

The terms usually preferred by people with this condition are "short-statured" or "little person" rather than ​dwarf. The term midget is now considered to be offensive by many people.

Categories of Dwarfism 

There are two main categories of dwarfism:

  • Disproportionate dwarfism: This means that a person has some average-sized parts of the body, such as the head and/or trunk, and some shorter-than-normal parts of the body, such as the legs and arms. The most common type of disproportionate dwarfism (and the most common type of dwarfism, in general) is achondroplasia, in which a person has a normal-sized torso and short limbs.
  • Proportionate dwarfism: This means that the person is smaller-than-average all over. Growth-hormone deficiency dwarfism, primordial dwarfism, and Seckel syndrome are all types of proportionate dwarfism.

The types of dwarfism have different causes and physical characteristics, though all affected by these conditions are short. Most of the conditions are genetic and present at birth.

Achondroplasia—The Most Common Type of Dwarfism

Achondroplasia makes up 75 percent of all cases of dwarfism and occurs in one out of every 15,000 to 40,000 births. With achondroplasia, there is a problem with the gene that tells the body to convert cartilage to bone while growing (especially in the long bones). Physical traits of this type of dwarfism include:

  • The upper body is of average size but the arms and legs are noticeably shorter.
  • The head is usually larger than average.
  • The forehead is prominent.
  • The fingers are typically shorter than average.
  • Adults can develop an arch of the lower back or bowed legs.
  • The average height for an adult is a little over 4 feet.

Causes of Dwarfism

The majority of people with dwarfism experience gene mutations (changes in specific genes) that interfere with the normal development of the cartilage and bones in the body. Since arms and legs have the longest bones, any interference in normal bone development usually results in shorter limbs—leading to short stature.

The genetic change that causes dwarfism is either passed down from parent to child (inherited) or happens when a mutation (gene change) takes place in the egg or sperm cell before conception. Two short-statured people can have a non-dwarf child, while average-sized parents can give birth to a child with achondroplasia.

Some non-genetic types of dwarfism can be caused by a growth hormone deficiency or they can occur if a baby or child's body does not get the nutrients that are needed for growth and proper development. These cases are usually treatable by a specialist.

Getting a Diagnosis

Most cases of achondroplasia can be diagnosed before birth (through the use of ultrasound in the later stages of pregnancy). Ultrasounds can show shorter-than-average arms and legs, as well as whether the baby's head is larger than average.

There are some types of dwarfism that can be diagnosed even earlier in pregnancy and there are other types that can't be diagnosed until after birth. 

There is no cure available for dwarfism caused by genetic disorders. Preventing or treating accompanying health concerns is the only course of action available at this time for little people and their families.

If a child doesn't receive a diagnosis of dwarfism, he or she may simply be on the short side of the normal growth spectrum.

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