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 (122 cm). The main reason for dwarfing conditions is frequently referred to as short-limb or short-trunk types. Achondroplasia, hypochondroplasia, and metaphyseal chondrodysplasias are considered short-limb dwarfing conditions. The primary defect found in patients with achondroplasia is abnormal endochondral ossification. The iliac crest apophyses are normal, giving rise to large, square iliac wings. Approximately 10,000 individuals are estimated to have achondroplasia. It affects about 1 in every 40,000 children. The worldwide population of little people is approximately 190,000. The standardized mortality ratio is increased for all age groups by a factor of 2.27 over that of the general population. In individuals aged 5-24 years, central nervous system and respiratory abnormalities are the common causes of death.