What causes achondroplasia?

Achondroplasia is inherited by an autosomal dominant gene that causes abnormal cartilage formation. Autosomal dominant inheritance means that the gene is located on one of the autosomes (chromosome pairs 1 through 22). This means that males and females are equally affected. Dominant means that only one gene is necessary to have the trait. When a parent has a dominant trait, there is a 50 percent chance that any child they have will also inherit the trait. So, in some cases, the child inherits the achondroplasia from a parent with achondroplasia. The majority of achondroplasia cases (80 percent), however, are the result of a new mutation in the family - the parents are of average height and do not have the abnormal gene.

As mentioned, persons with achondroplasia have a 50 percent chance to pass the gene to a child, resulting in the condition. If both parents have achondroplasia, with each pregnancy, there is a 50 percent chance to have a child with achondroplasia, a 25 percent chance that the child will not inherit the gene and be of average height, and a 25 percent chance that the child will inherit one abnormal gene from each parent, which can lead to severe skeletal problems that often result in early death.

Geneticists have found that fathers who are older than 45 have a higher chance of having children with certain autosomal dominant conditions such as achondroplasia, but no cause for the new mutations in sperm has been discovered at this time.

The gene responsible for achondroplasia was discovered in 1994 making accurate prenatal diagnosis available, in most cases.

Please see the webpages for more details on Achondroplasia.

Achondroplasia is inherited by an autosomal dominant gene that causes abnormal cartilage formation. Autosomal dominant inheritance means that the gene is located on one of the autosomes (chromosome pairs 1 through 22). This means that males and females are equally affected. Dominant means that only one gene is necessary to have the trait. When a parent has a dominant trait, there is a 50 percent chance that any child they have will also inherit the trait. So, in some cases, the child inherits the achondroplasia from a parent with achondroplasia. The majority of achondroplasia cases (80 percent), however, are the result of a new mutation in the family - the parents are of average height and do not have the abnormal gene.