Achondroplastic Dwarfism: An Overview
Achondroplastic dwarfism is one of the most common types of dwarfism. The term
achondroplasia is a Greek word that means "without cartilage formation." People with achondroplastic dwarfism 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 Achondroplastic Dwarfism?
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 Achondroplastic Dwarfism?
Most people with achondroplastic dwarfism have average-size parents, which means that achondroplasia is caused by a new mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. This altered FGFR3 gene is responsible for achondroplastic dwarfism. Scientists do not know why this mutation occurs.
(Click FGFR3 Gene for more information about the gene that can cause achondroplastic dwarfism.)
Achondroplastic dwarfism can also be inherited in an autosomal dominant pattern, meaning that 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 achondroplastic dwarfism, 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.
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