Most dwarfism-related conditions are genetic disorders, but the causes of some disorders are unknown. Most occurrences of dwarfism result from a random genetic mutation in either the father's sperm or the mother's egg rather than being in either parent's complete genetic makeup.

Achondroplasia

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. A person with the disorder may pass along either a mutated or normal copy to his or her own children.

Turner syndrome

Turner syndrome occurs because of a random deletion or severe alteration of an X chromosome either in the sperm or egg. The X chromosome is one of two chromosomes that determine the sex of a person. A female inherits an X chromosome from each parent, and a male inherits a Y chromosome from his father and an X chromosome from his mother. A girl with Turner syndrome has only one fully functioning copy of the female sex chromosome rather than two.

Growth hormone deficiency

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.

Other causes of dwarfism include deficiencies in other hormones and poor nutrition.

Aug. 27, 2011

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