Dwarfism is short stature that results from a genetic or medical condition. Dwarfism is generally defined as an adult height of 4 feet 10 inches (147 centimeters) or less. The average adult height among people with dwarfism is 4 feet. The disorders are divided into two broad categories: Disproportionate dwarfism where the body size is disproportionate, some parts of the body are small, and others are of average size or above-average size. Disorders causing disproportionate dwarfism inhibit the development of bones. Proportionate dwarfism where the body is proportionately small if all parts of the body are small to the same degree and appear to be proportioned like a body of average stature. Medical conditions present at birth or appearing in early childhood limit overall growth and development. Dwarfism can be caused by any of more than 200 conditions. Causes of proportionate dwarfism include metabolic and hormonal disorders such as growth hormone deficiency. Most dwarfism-related conditions are genetic disorders, but the causes of some disorders are unknown. About 80 percent of people with achondroplasia are born to parents of average height. A person with achondroplasia and with two average-size parents received one mutated copy of the gene associated with the disorder and one normal copy of the gene. Turner syndrome, a condition that affects only girls and women, results when a sex chromosome (the X chromosome) is missing or partially missing. The cause of growth hormone deficiency can sometimes be traced to a genetic mutation or injury, but for most people with the disorder, no cause can be identified.
The characteristic features of the skull, spine and limbs shared by most forms of disproportionate dwarfism result in some common problems like delays in motor skills development, such as sitting up, crawling and walking, frequent ear infections and risk of hearing loss, bowing of the legs, difficulty breathing during sleep (sleep apnea), pressure on the spinal cord at the base of the skull, excess fluid around the brain (hydrocephalus), crowded teeth progressive severe hunching or swaying of the back with back pain or problems breathing, arthritis, weight gain that can further complicate problems with joints and the spine and place pressure on nerves. Women with disproportionate dwarfism may develop respiratory problems during pregnancy.
Most dwarfism treatments don't increase stature but may correct or relieve problems caused by complications. Surgical procedures that may correct problems in people with disproportionate dwarfism include correcting the direction in which bones are growing, stabilizing and correcting the shape of the spine, increasing the size of the opening in bones of the spine (vertebrae) to alleviate pressure on the spinal cord. For individuals with dwarfism due to growth hormone deficiency, treatment with injections of a synthetic version of the hormone may increase final height. Treatment for girls with Turner syndrome also requires estrogen and related hormone therapy in order for them to begin puberty and achieve adult sexual development. Estrogen replacement therapy usually continues throughout life until a woman reaches the average age of menopause.