Achondroplasia

A rare genetic disorder of bone growth that leads to short stature. The condition is caused by a dominant gene (see genetic disorders) but often arises as a new mutation. The long bones of the arms and legs are affected mainly. The cartilage that links each bone to its epiphysis (the growing area at its tip) is converted to bone too early, preventing further limb growth. Those affected have short limbs, a welldeveloped trunk, and a head of normal size except for a protruding forehead.