The Most Common Types of Dwarfism

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Dwarfism is a condition characterized by short stature, usually resulting in an adult height of four-feet, 10-inches or shorter. For children, this means being below the height growth curve for their age, which would be less than the 3rd percentile.

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

Types of Dwarfism
Verywell / Jessica Olah

Types

More than 300 different conditions can cause dwarfism. The types of dwarfism have different causes and physical characteristics, though they are all characterized by short stature. Most of the conditions are genetic and present at birth. There are two main categories of dwarfism:

  • Disproportionate Dwarfism: This means that a 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—and the most common type of dwarfism in general—is achondroplasia, in which a person has a normal-size 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.

Dwarfism is a relatively rare condition, and each of the individual types of dwarfism is even rarer.

Achondroplasia

Achondroplasia makes up 70% of all cases of dwarfism and affects about one of every 25,000 to 30,000 newborns. With achondroplasia, there is a problem with the gene that allows the body to convert cartilage to bone while growing, especially in the long bones. Physical traits of this type of dwarfism include:

  • Relatively long trunk
  • Short arms and legs
  • Short hands and fingers, with the ring and middle finder
  • Disproportionately large head with a prominent forehead
  • Large, prominent forehead
  • Bowed legs
  • Curved spine

Many people who have achondroplasia have hydrocephalus, which is fluid in the brain. Typically, hydrocephalus associated with achondroplasia is mild, but if it is severe or persistent, a shunt can be placed. Some people with achondroplasia also have apnea or sleep apnea, which is periodic episodes of interrupted breathing.

Other

Examples of other types of dwarfism include:

Causes

Dwarfism can be caused by a genetic condition, or by a medical or hormonal condition.

  • Mutations: The majority of people with dwarfism have gene mutations, which are changes in specific genes. These mutations interfere with the normal development and may affect the growth 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, which leads to short stature.
  • Genetics: Any genetic change that causes dwarfism can be inherited from parents, or it may develop during fetal development. There are a number of different inheritance patterns because there are so many different causes of dwarfism. Two short-statured people can have a non-dwarf child, while average-sized parents can give birth to a child with achondroplasia.
  • Medical Causes: 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.

Diagnosis

There are some types of dwarfism that can be diagnosed early in pregnancy with genetic testing.

Some cases of achondroplasia can be diagnosed in the late stages of pregnancy through the use of ultrasound.

Ultrasounds can show shorter-than-average arms and legs, as well as whether the growing baby's head is larger than average. Often, however, dwarfism can't be diagnosed until after birth. 

Treatment

Dwarfism itself is not a disease and therefore there is no "cure." Most people with the condition have normal intelligence and lead healthy, active lives. However, the conditions that cause dwarfism can cause health complications, particularly those involving the spine and lower limbs.

Some medical issues are treated with surgery, usually on the back, neck, leg, foot, or middle ear.

Prevention and treatment of these health problems can help improve quality of life and survival.

If a child is very short, he or she might not receive a diagnosis of dwarfism if there are no other features besides short stature. Many people who are on the short side of the normal growth spectrum do not have dwarfism.

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Article Sources

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  2. National Center for Advancing Translational Sciences. Genetic Rare Diseases Information Center. Dwarfism. Updated May 19, 2011.

  3. Pauli RM. Achondroplasia: a comprehensive clinical review. Orphanet J Rare Dis. 2019;14(1):1. doi:10.1186/s13023-018-0972-6

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