Types of Dwarfism: What Is the Most Common Kind?

Learn More About How This Genetic Condition Is Caused

ndian Jyoti Amge, 19, the world's shortest woman according to the Guinness Book of Records, poses for pictures during an event in Kuwait City, on March 14, 2013.
Kuwait-Guinness-Record. Credit: Yasser Al-Zayyat / Stringer / 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 now considered offensive and derogatory). "Short-statured" or "little person" are the preferred terms referral for most people with dwarfism.

Categories of Dwarfism 

There are 2 main categories of dwarfism:

  • Disproportionate dwarfism, meaning that the person has some average-size 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 is achondroplasia. In fact, achondroplasia accounts for about 70% of all cases of dwarfism.
  • The other main category of dwarfism is proportionate dwarfism, meaning that the person is small all over. Growth-hormone deficiency dwarfism, primordial dwarfism, and Seckel syndrome are types of proportionate dwarfism.

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

Most Common Type

Making up almost 75% of all cases is Achondroplasia, a type of dwarfism that occurs in 1 of every 15,000 to 40,000 births.

With Achondroplasia, there is a problem with the gene that tells your body to convert cartilage to bone while growing (especially in the long bones). Physical traits of this type include:

  • An average-size 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 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 caused dwarfism was either passed from parent to child (inherited) or happened when a mutation (gene change) took 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 achiachondroplasia.

Some non-genetic types of dwarfism can be caused by a growth hormone deficiency or 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.

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, or whether the baby's head is larger than average.

There are other 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. Prevention and treatment of accompanying health concerns are the only course of action available at this time for little people and their families. 

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