Inheritance Pattern of Achondroplasia
Achondroplasia occurs when cartilage has difficulty converting to bone, which usually results in dwarfism. There are two possible causes of achondroplasia:
- A mutation in the fibroblast growth factor receptor 3 (FGFR3) gene
- Inheriting the gene from a parent with achondroplasia.
In the second cause, the inheritance pattern of achondroplasia occurs in an autosomal dominant pattern, which means that one copy of the altered gene in each cell is sufficient to cause the disorder. Therefore, if one of the parents with achondroplasia passes the FGFR3 gene on to the child, the child will likely develop the condition.
If one parent has achondroplasia, a child has a 50 percent chance of inheriting the FGFR3 gene (located on chromosome 4) and subsequently developing achondroplasia. If both parents have the disorder, the child has a three in four (75 percent) chance of developing achondroplasia. Also, in these cases, the child has a one in four chance of inheriting the gene from both parents. Newborns who inherit both genes are considered to have a severe form of achondroplasia, where survival is usually less than 12 months after birth.
(Click Achondroplasia Genetics to read more detailed information on the FGFR3 gene and how it mutates.)