There are many causes of dwarfism in humans, Achondroplasia (one of over 500 skeletal dysplasias) is the most frequently diagnosed.
Approximately 1 in 40,000 children are affected, and there seems to be no gender bias.
Acceptable terms for referring to a person born with dwarfism include: dwarf, little person (oppose big person) and short-statured. Terms like midget, shrimp, etc., are very offensive and outdated.