Achondroplasia is an inherited disorder of bone growth that affects from 1 in 15,000 to 1 in 40,000 live births. It is not associated with any specific ethnic group. Although achondroplasia literally means "without cartilage formation," in this disorder the problem is not in forming cartilage but in converting it to bone, especially in the long bones of the arms and legs. All people who have achondroplasia are short. The average height of an adult male with achondroplasia is 131 cm (52 inches, or 4 foot 4), and the average height for adult females is 124 cm (49 inches, or 4 foot 1). A person with achondroplasia has an average-size torso, short arms and legs with disproportionately short upper arms and thighs, a slightly enlarged head, and a prominent forehead.

People with achondroplasia are generally of normal intelligence. Health problems associated with achondroplasia can include breathing problems, obesity, and ear infections. The head is usually large and may have enlarged fluid spaces within the brain. Adults with achondroplasia usually develop a pronounced and permanent sway of the lower back and bowed legs. Older individuals often have back pain, which can cause difficulty with walking.

Achondroplasia is caused by changes in a persons DNA (called mutations) in the gene called FGFR3 that causes achondroplasia. This gene plays a role in the development and maintenance of bone and brain tissue. Researchers believe that mutations in the FGFR3 gene cause the receptor to be overly active, which interferes with the way that cartilage gets converted to bone, and leads to the disturbances in bone growth seen with this disorder. This is one major are a of research.

Achondroplasia is inherited through families in autosomal dominant pattern, which means only one copy of the altered gene or DNA is necessary to cause the disorder. Most people with achondroplasia have average-size parents. In these cases, a mutation in the FGFR3 gene occurred in one parent's egg or sperm cell before conception. Other people with achondroplasia inherited it from a parent who has the condition. Research on achondroplasia would be funded and organized by a number of different government and private organizations like the National Institutes of Health (NIH, Centers for Disease Control and Prevention (CDC) and the National Organization for Rare Disorders (NORD).