Genetics Home > Achondroplastic Dwarfism
Achondroplastic dwarfism is a disorder in which cartilage has difficulty converting to bone. This is especially noticeable in the long bones of the arms and legs, leading to a short stature in those with this condition. It can be inherited or the result of a new mutation in the FGFR3 gene. While there is no cure, treatments are available to manage the signs, symptoms, and health conditions that occur as a result.
Achondroplastic Dwarfism: An OverviewAchondroplastic dwarfism is one of the most common types of dwarfism. The term achondroplasia is a Greek word that means "without cartilage formation." People with this condition are typically short in stature with proportionately short arms and legs. They also tend to have a large head, a prominent forehead, and a flattened bridge of the nose.
What Is It?Achondroplastic dwarfism is a bone growth disorder. Although achondroplasia literally means "without cartilage formation," the problem is not the forming of cartilage. The problem occurs when cartilage has difficulty converting to bone, especially in the long bones of the arms and legs.
What Causes the Condition?Most people with this disorder have average-size parents, which means that achondroplasia is caused by a new mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. Scientists do not know why this mutation occurs (see FGFR3 Gene for more information).
Achondroplastic dwarfism can also be inherited in an autosomal-dominant pattern, which means one copy of the altered gene in each cell is enough to cause the disorder. In these cases, one of the parents with achondroplasia passes the FGFR3 gene on to the child. If one parent has achondroplastic dwarfism, their children have a 50 percent chance of inheriting the FGFR3 gene.
If both parents have the condition, their children have a 25 percent chance of inheriting the gene from both parents. Newborns who inherit two copies of the altered FGFR3 gene are considered to have a severe form of achondroplasia, where survival is usually less than 12 months after birth.
(Click Cause of Achondroplasia for more information.)