Dwarfism is the condition that exists when a plant or animal is much smaller than others of its kind. Dwarfism occurs both in individuals and in entire groups of living things. The smallest species of a particular group is often referred to as a dwarf. There are several dwarf animal breeds, varieties, and species, such as dwarf cattle and dwarf lemurs. Many ornamental fruit trees are actually dwarf varieties of larger plant species, as are several varieties of flowers, such as dahlias and marigolds.
Some human groups called Pygmies are characterized by short stature. However, most anthropologists do not consider them to be true dwarfs. Homo floresiensis, a prehistoric humanlike creature that is small in stature, is thought to be an extinct dwarf species.
The word dwarf comes from a Germanic word. It describes an ancient race of tiny humans who worked with metals to make magical objects. Cultures throughout the world have myths about ”little people.” These little people, who are often mischievous in nature, come in many forms, such as brownies, elves, gnomes, and leprechauns. The remainder of this article discusses dwarfism as a condition in individual humans.
Causes.
Medical experts recognize more than 200 conditions that can cause human dwarfism. Many of these conditions affect growth of the skeleton and the formation of a tough, rubbery tissue called cartilage. Other factors that affect human growth include diet, general health, hormone levels, physical activity, and sleep. Any condition that modifies or interferes with these factors can cause dwarfism.
Some forms of dwarfism result from low levels of somatotropin, the body’s main growth hormone. Somatotropin is one of several hormones produced by the pituitary gland, a pea-sized gland that lies under the brain near the center of the skull. An excess or deficiency of somatotropin causes abnormal growth and development. Children diagnosed with somatotropin-deficient dwarfism, also called pituitary dwarfism, can be treated with artificial growth hormone. However, treatment is usually expensive.
Other types of dwarfism are genetic in nature. They are caused by mutations (changes) in genes that play a role in regulating growth. Genes help determine what characteristics living things develop from their parents. The most commonly recognized genetic form of dwarfism is achondroplasia. In this condition, the gene-regulated process that converts cartilage to bone during growth is disrupted. People with achondroplasia typically have short arms and legs, with an average-sized head and trunk. Achondroplasia may be inherited from a parent with the condition. However, most cases result from a mutation occurring among parents of average stature. Diastrophic dwarfism is a less common genetic form. This condition is recessive—that is, an individual must inherit the diastrophic gene from each parent to develop the condition. The mutation affects the pattern of cartilage and bone growth, resulting in greatly shortened limbs, fingers, and toes.
Both achondroplastic and diastrophic dwarfism are examples of chondrodisplasia—that is, a nontypical pattern of cartilage and bone growth. Some children with chondrodisplasia are treated by limb lengthening. In this process, doctors surgically cut the long bones and progressively stretch the bone halves apart over time as the bones grow back together. This long and painful procedure can lengthen each bone 2 to 4 inches.
A rare condition called primordial dwarfism results in the smallest human dwarfs. Primordial dwarfs have average limb proportions, but they are extremely small. Scientists believe this type of dwarfism is caused by an unknown genetic mutation.
Living with dwarfism.
People with dwarfism may encounter a variety of physical and social challenges. Throughout history, people of typical height have viewed people with dwarfism with curiosity, prejudice, ridicule, and even fear. Today, attitudes about dwarfism have changed. Such organizations as Little People of America and the Dwarf Athletic Association of America provide support and information to people with dwarfism and their nondwarf families and friends.
Most people with dwarfism have generally good health and an average life span. However, discrimination remains common. In the United States, the Americans with Disabilities Act classifies dwarfism as a disability for civil rights protection. But people with dwarfism tend to report the same levels of life satisfaction as people without.
See also Bonsai; Pygmies; Shetland pony; Toy dog.
