Dwarfism is a condition that occurs when an animal has a short stature. In humans, it is defined as an adult with a height of 4 feet 10 inches or less. The two main groups of dwarfism are: proportionate and disproportionate. In proportionate group, the parts of the body are proportionate. Disproportionate dwarfs have shorter legs and arms and average-size trunk.
In most cases, dwarfism is caused by genetic disorder. Most dwarfism occurrences result from the genetic mutation in the mother’s egg or the father’s sperm rather than from complete genetic makeup of either parent.
The common genetic disorders that cause dwarfism are achondroplasia, turner syndrome and growth hormone deficiency. About 80% of individuals with achondroplasia condition are born to normal parents. A person with achondroplasia received one mutated gene linked with the condition and one normal copy of the gene. An individual with the disorder may pass either normal or mutated copy to his/her own children.
Turner syndrome affects only women and girls. It results when the X chromosome is missing. A girl with this disorder has one fully functioning copy of the X chromosome rather than two. Finally, the deficiency of growth hormone can sometimes be traced to an injury or genetic mutation.