Dwarfism is disproportionate short stature, resulting from any of several gene mutations that cause impaired and dyssynchronous growth of the skeleton. In addition to short stature, impaired skeletal development, called skeletal dysplasia, can lead to deformation of the spine, with compression of underlying nervous tissue, or to poorly mobile joints prone to premature osteoarthritis. In certain forms of dwarfism, there is also involvement of nonskeletal structures, usually the eyes, or less often, the immune system or the brain.
Several hundred forms of dwarfism have been recognized. One general class, short-trunk dwarfism, results from impaired growth of vertebrae. Impairment of the growth of long bones causes short-limb dwarfism, classified further by designating the limb segment most affected, either the root, middle, or distal portion of the bones. The genes responsible for many types have been identified.
The majority of individuals affected with dwarfism enjoy an independent life, with a normal life span. Some consider the term dwarf pejorative, preferring to be called "little people."