Achondroplasia is a genetic disorder that causes short stature called dwarfism and a large head, also known as macrocephaly. It is a disorder in which bone and cartilage do not grow normally. It is the most common cause of dwarfism.

This condition leads to patients reaching a full-grown height of less than four feet. The greatest shortening occurs in the bone between the shoulder and the elbow and the bone between the hip and the knee. There may also be underdevelopment of the face.

Achondroplasia is a genetic disorder. It is caused by mutations in the FGFR3 gene. This gene prevents the growth of cartilage at the growth plate. FGFR3 encodes a protein called Fibroblast Growth Factor Receptor 3. This protein is the site of action of a major growth factor responsible for lengthening bones. When this growth factor cannot act properly due to the absence of its receptor, the growth of bones, at the growth plate's cartilage, is slowed. This leads to shorter bones, abnormally shaped bones, and shorter stature.

The gene for achondroplasia can be passed from one generation to the next. If a parent has the disorder, there is a 50% chance of passing the gene for achondroplasia to children. In most cases of achondroplasia, it more commonly is the result of a sudden genetic defect that occurs in the developing embryo.