Types of Dwarfism

Types of Dwarfism

More than 200 medical conditions have been identified as causes of dwarfism or short stature, out of which bone deformity and hormonal disorders are the primary causes. This HealthHearty article explains the different types of dwarfism that are categorized and named according to the underlying medical cause.
HealthHearty Staff
Last Updated: Mar 1, 2018
Children measuring height
Dwarfism is a medical condition that causes a person to remain short in stature throughout his/her life, irrespective of his/her age. As per the protagonism group, little people of America (LPA), an adult having a height of 4 feet 10 inches (147 cm) or below is said to be affected by dwarfism. However, as the height of individuals varies significantly with respect to gender and race, this specific height measurement is not applicable for demarcating people with dwarfism from the rest of population. An individual of short stature is also referred to as a 'little person'. For better understanding on dwarfism, let's discuss more about its causes and types.

Causes
In majority of the people affected by dwarfism, hereditary factor is the leading cause. There are a myriad medical conditions (more than 200) that can result in this height disorder. Nevertheless, the causes are not necessarily a genetic disorder or a disease. It is just that the genetic component of the sperm cells or the egg cells undergo spontaneous mutation prior to conception. Other dwarfism causes are inherited genes from the parents, chromosomal abnormalities (e.g., turner syndrome), growth hormone deficiency, malabsorption, and other chronic diseases.

Considering these causes, it is quite possible that average-sized parents can give birth to a dwarf child. In fact, most children of dwarfism are born to average height parents. Similarly, children of short stature parents can be average-size and tall. In the latter case, a genetic counselor is the best person to consult regarding the chances of passing the genetic traits (responsible for dwarf character) to the offspring.

Types of Dwarfism

When speaking about types of dwarfism, classification is based on the underlying cause of the problem. The two main categories are disproportionate dwarfism and proportionate dwarfism. The former type causes abnormal development of the body parts, usually short arms and legs with a normal size torso. In such a case, there is impairment in the development of bones. In proportionate dwarfism, nearly all the body parts are proportionately small, giving a proportioned body stature. Besides these, there are several other types.

We shall take a look at some of the most common types of causes. All these causes are, at the end of the day, the primary reason for all the conditions that occur.

Achondroplasia
This skeletal dysplasia is by far the most common type of dwarfism. In fact, more than 70 percent of dwarfism account to achondroplasia and about 85 percent children with achondroplasia are born to average-size parents. People with achondroplasia have a long torso, short limbs, large head, and lack of muscle. According to statistics, in every 25,000 people, one person is affected with this type.

Diastrophic Dysplasia
Diastrophic dysplasia is a relatively less common type of dwarfism. It is estimated that one out of 100,000 children are born with diastrophic dysplasia. People affected with this type tend to have a cleft palate, shortened limbs, ear deformity, club feet, joint stiffness, and reduced muscles.

Spondyloepiphyseal Dysplasia (SED)
Spondyloepiphyseal dysplasia is a rare genetic disorder that causes dwarfism. Similar to other skeletal dysplasia, here, the growth of the bone is disturbed, resulting in a short stature. The characteristic features of spondyloepiphyseal dysplasia is a short trunk, short neck, abnormal limb length, severe spinal curvature, cleft palate, and club feet. About one in 95,000 newborns are affected with this type.

Primordial Dwarfism
It is a rare and severe type of dwarfism, in which the body size is comparatively small right from birth. Primordial form is categorized under the proportionate type of dwarfism and is difficult to diagnose before the child attains three to five years of age. Based on the cause, there are five primordial dwarfism types, namely seckel syndrome, osteodysplastic primordial dwarfism type I (ODPDI), osteodysplastic primordial dwarfism type II (ODPDII), Russell-Silver syndrome, and Meier-Gorlin syndrome. People affected with this type usually have a short life (hardly 30 years).

Pseudoachondroplasia
It is a form of skeletal dwarfism, in which the arms and legs are abnormally short. The growth rate is usually normal in the early stages (up to 3 years), after which the child displays a stunted growth with delay in motor skills and a waddling posture. Knee deformities and arthritis at an early age are major complications for this type.

Hypochondroplasia
Hypochondroplasia accounts to the tallest height among dwarfs. It is caused by the mutations in the FGFR3 gene. On an average, the adult height measures from 125―160 cm. The bodily features include the appearance of having a large head due to under-developed body parts, limited motion of elbows, and bowed legs. In most cases, only the extremities and fingers tend to develop short. However, in some cases, people with hypochondroplasia may also have a normal appearance. About one in 15,000-40,000 newborns may be affected with hypochondroplasia.

Pituitary Dwarfism
Pituitary dwarfism is caused due to improper functioning of the pituitary gland. People with this type have a short stature but with proportionate body parts. Hence, it is categorized under proportionate dwarfism. Some experience delayed puberty and possess reproductive capabilities, while many others are sterile.

Osteogenesis Imperfecta
Osteogenesis imperfecta refers to the rare genetic disorder characterized by defect in the genes responsible for synthesis of type I collagen, a major component of bones and other connective tissues. As a result the quantity and/or quality of the collagen produced in the body is compromised which leads to fragile or brittle bones. The individual generally has a short stature, bone deformities, scoliosis, brittle teeth, as well as hearing and breathing difficulties. It is also known as brittle bone disease or Lobstein syndrome. It occurs in about one in 20,000 newborns.

Turner Syndrome
Tuner syndrome is also a genetic disorder, in which absence of parts or the complete pair of X chromosome is the most common cause. One of the notable features of this genetic disorder is short stature or dwarfism. Other characteristics associated with turner syndrome are a webbed neck, broad chest, distinctive ears, and gonadal dysfunction. It is estimated that one out of 2500 baby girls are affected with turner syndrome.

Psychogenic or Psychosocial Dwarfism
Psychogenic dwarfism, as the name signifies, is manifested as a result of extreme stress during childhood (above two years). In such a case, there is less secretion of the growth hormone, which ultimately causes a short stature. Other symptoms of psychogenic dwarfism include inappropriate height and weight, immature bone age and generative cognitive ability.

These are some of the common forms of dwarfism. As already mentioned, there are around 200 medical reasons that are responsible for causing dwarfism. In majority of the cases, you will find bone abnormality and hormonal irregularity as the primary factors for dwarfism.

An Overview

There is no doubt that dwarfism is not an intellectual impairment, and a little person has typically the same IQ level as that of a normal-size person. But there are certain health complications that may be associated with a child born with dwarfism. Lack of muscle, medically referred to as hypotonia, is a common condition that is observed in most people affected with dwarfism. Other medical complications include delaying motor skills, breathing problems, painful joints and back, arthritis, frequent ear infections, crowding of teeth, and weight problems.

With the advancement in medical science and human genetics, certain effective interventions have been developed for alleviating the health complications accompanied with dwarfism. For nearly all the dwarfism types, timely diagnosis of the underlying cause and proper medical attention are the thumb rules to lead a normal, healthy, and long life.