Types of Dwarfism: Which Is Most Common?

Pregnant woman having ultrasound scan
Diagnosing Dwarfism. Andersen Ross / Getty Images

There are an estimated 200 types of dwarfism. Dwarfism means that a person has an adult height of 4 feet, 10 inches or shorter.

In the past, a person who was very small in stature was called a "midget" (a term that's now considered offensive). "Short-statured" and "little person" are now the preferred terms for people with dwarfism.

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 called achondroplasia, in which a person has a normal-sized torso and short limbs. (For more details about achondroplasia, keep reading.)

Different types of dwarfism have different causes and different physical characteristics, though all dwarfs are short. More than 300 different medical conditions (which are mostly genetic and present at birth) have been known to cause dwarfism.

The Most Common Type 

Making up almost 75 percent of all cases of dwarfism is achondroplasia, a type of dwarfism that 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:

  • An average-sized upper body, but noticeably shorter arms and legs
  • The head is usually larger than average
  • A prominent forehead
  • The fingers are typically shorter than average
  • Adults can develop an arch of the lower back or bowed legs
  • 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 a short stature.

The genetic change that causes dwarfism is either passed from parent to child (inherited) or happens when a mutation (gene change) takes place in the egg or sperm cell prior to 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 an 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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