Achondroplasia

Inheritance

How can we avoid having a baby with the fatal type of achondroplasia?

When both parents have achondroplasia, there is a 1 in 4 risk that any baby conceived would inherit both parents' FGFR3 gene mutations. This combination of two FGFR3 mutations is not compatible with life. There are some options for parents. Parents can pursue preimplantation genetic diagnosis (PGD). With PGD, using in vitro fertilization and genetic testing technologies, parents can choose to not implant embryos that have two FGFR3 mutations into the mother's uterus. PGD is relatively expensive and may not be covered by insurance. Furthermore, it is not guaranteed to lead to pregnancy every time nor is it guaranteed to ensure having babies that are unaffected with the fatal form of achondroplasia.

Another option for parents hoping to avoid having offspring with the fatal form of achondroplasia caused by inherited the abnormal FGFR3 gene change from both parents is prenatal diagnosis. DNA from the baby can be tested during the pregnancy to determine how many FGFR3 mutations a baby has. This can be done in the first trimester (around 10-13 weeks) by a procedure called chorionic villus sampling or in the second trimester (after 15 weeks) by amniocentesis.

To learn more about PGD or prenatal diagnosis, contact a genetic counselor near you. To find a genetic counselor near you, visit the National Society of Genetic Counselors Find a Genetic Counselor website.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
Show More Content Like This

More Inheritance Content

What is the chance to have another baby with achondroplasia if both parents are unaffected?

How is achondroplasia inherited?

What does it mean to have a 'variant' in the gene for achondroplasia?

What is the chance of a baby having achondroplasia when both parents have it?

What is the chance to have another baby with achondroplasia if both parents are unaffected?

When a couple, neither of whom have achondroplasia, have a baby with achondroplasia, the genetic change occurred for the first time in that baby. This is known as a de novo gene change. When a genetic change is de novo, it is unlikely to occur again in a future pregnancy. There are rare instances, however, of an unaffected couple having more than one affected baby. This is due to a condition known as germline, or gonadal, mosaicism. In gonadal mosaicism, a gene change can be found in the reproductive cells (sperm or egg cells) of an individual that is not present in the cells of the rest of their body. Individuals with germline mosaicism can produce multiple egg or sperm cells that carry a gene change. Although low, therefore, there is a slightly increased risk for an unaffected couple to have subsequent offspring with achondroplasia. This chance likely does not exceed 1% with each pregnancy.

References
  • Trotter, T.L., Hall, J.G., Health Supervision for Children with Achondroplasia. American Academy of Pediatrics. 2005; 116: 3: 771- 783;http://www.lpaonline.org/assets/documents/Health%20Supervision%20for%20Children%20With%20Achondroplasia.pdf
  • https://www.ncbi.nlm.nih.gov/books/NBK1152
How is achondroplasia inherited?

Although achondroplasia is a genetic condition, when a person has achondroplasia, it is not always inherited from a parent. In fact, only about 20% of people with achondroplasia inherited it from either their mom or dad. The other 80% of the time, achondroplasia is a new diagnosis in the family and was not inherited from either parent. In this case, there was a spontaneous change in the FGFR3 gene carried by the egg or sperm cell that helped conceive that individual. That gene change is present from the time the baby is conceived and causes the abnormal bone development seen in achondroplasia. Because the affected individual carries that gene change in all of the cells of their body, their own future offspring are at risk for achondroplasia.

If a person with achondroplasia has a baby with a person who is unaffected, there is a 50% chance that any offspring will have achondroplasia. This means that when one parent is affected there is also a 50% chance that the baby will not have achondroplasia.

When both parents have achondroplasia, there is still a 50% chance that any child they have will have achondroplasia. There is a 25% chance that any child will not inherit achondroplasia. This means that the child inherited neither parent's changed copy of the FGFR3 gene. There is also a 25% risk that any child whose parents both have achondroplasia could inherit both parents' changed copy of the FGFR3 gene. Unfortunately, babies with two copies of the FGFR3 gene mutation do not survive.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
  • https://ghr.nlm.nih.gov/condition/achondroplasia#inheritance
What does it mean to have a 'variant' in the gene for achondroplasia?

Over 99% of people with achondroplasia have one of two genetic changes in the FGFR3 gene: c.1138G>A (p.Gly380Arg) or c.1138G>C (p.Gly380Arg). Other changes in to the FGFR3 gene may be classified as a "variant of uncertain significance." This means that it is a genetic change that we do not fully understand and that we are not quite sure if or how it affects the body. It may cause achondroplasia and it may not. We need more data to be sure. A genetic counselor or geneticist may be able to help explain what this result means for your particular situation. To find a genetic counselor near you, visit the National Society of Genetic Counselors Find a Genetic Counselor website.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
  • http://www.nchpeg.org/microarray/what-do-other-results-mean
What is the chance of a baby having achondroplasia when both parents have it?

When both parents have achondroplasia, there is a 50% chance that any child they have will have achondroplasia. There is a 25% chance that any child will not inherit achondroplasia. This means that the child inherited neither parent's changed copy of the FGFR3 gene. There is also a 25% risk that any child could inherit both parents' changed FGFR3 genes. Babies with two copies of the FGFR3 gene mutation are much more severely affected and have a low chance of survival due to their severe symptoms.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
  • https://ghr.nlm.nih.gov/condition/achondroplasia#inheritance

We use cookies to ensure that we give you the best experience on our website. By continuing to browse this site, you are agreeing to our use of cookies.

Continue Find out more about our use of cookies and similar technology

This content comes from a hidden element on this page.

The inline option preserves bound JavaScript events and changes, and it puts the content back where it came from when it is closed.

Remember Me