There are more than 200 conditions that cause dwarfism, including a mix of hormonal and metabolic disorders and genetic conditions. Skeletal dysplasia, which is the most common form of dwarfism, is a genetic or inherited condition that is characterized by abnormal growth of bones, according to WebMD.
There are several forms of skeletal dysplasia, but the most common is achrondroplasia, which is a type of dwarfism affecting one out of every 26,000 to 40,000 babies in the United States. Those suffering from this type of dwarfism have shortened upper parts of the legs and arms and a relatively long trunk with a large head characterized by a prominent forehead, protruding jaw and a flat nose. They also have flat, broad, short feet, bowed legs, and a forward-curving spine. Their teeth are generally misaligned and crowded, according to WebMD.
Less commonly, dwarfism is classified as spondyloepiphyseal dysplasia, and it affects one out of every 95,000 babies in the United States. Those with this form of dwarfism have shortened trunks, cleft palates, club feet, barrel-shaped chests, weak feet and hands, and severe osteoarthritis, according to WebMD.
Skeletal dysplasia is always caused by gene mutations. These mutations can be inherited, or they can occur spontaneously, according to WebMD. Most instances of dwarfism are readily discernible at birth.