There are an estimated 200 types of dwarfism. Dwarfism means that a person has an adult height of 4 feet 10 inches or shorter. There are two main categories of dwarfism.
One category is disproportionate dwarfism, meaning that the person has some average size parts of the body, such as the head and/or trunk, and some shorter-than-normal parts of the body, such as the legs and arms. The most common type of disproportionate dwarfism is achondroplasia. In fact, achondroplasia accounts for about 70 percent of all cases of dwarfism. The other main category of dwarfism is proportionate dwarfism, meaning that the person is small all over. Growth-hormone deficiency dwarfism a.k.a. pituitary dwarfism, primordial dwarfism, and Turner syndrome are types of proportionate dwarfism. Achondroplasia is a genetic disorder that impairs embryonic development, resulting in abnormalities in bone growth and cartilage development. It is one of a class of illnesses called chondrodystrophies, all of which involve cartilage abnormalities and result in short stature. Achondroplasia occurs in all races and with equal frequency in males and females and affects about one in every 40,000 children. In achondroplasia, the long bones fail to develop normally, making the arms and legs disproportionately short and stubby and sometimes curved. Overly long fibulae cause the bowlegs that are characteristic of the condition. In addition, the head is disproportionately large and the bridge of the nose is depressed. Persons with achondroplasia are 3–5 feet (91–152 cm) tall and of normal intelligence. Their reproductive development is normal, and they have greater than normal muscular strength. The condition occurs in one out of every 10,000 births, and its prevalence increases with the age of the parents, especially the father. Many infants with the condition are stillborn.
Turner syndrome is a chromosomal abnormality occurring only in females in whom one of the X