Achondroplasia

Diagnosis and Testing

What types of tests should be done for achondroplasia?

To confirm that someone has achondroplasia and not a different genetic cause for their short stature and health issues there are a few different types of tests:

Testing

Before birth

If there are some findings on the ultrasound or sonogram that makes the doctor think about achondroplasia, depending on how far along in the pregnancy the woman is, they may suggest a special genetic testing on a sample of amniotic fluid. This testing would be collected through an amniocentesis which is an invasive test. That would require planning to make sure the correct test was done because there are several testing options from panels like the prenatal skeletal dysplasia testing panel at http://www.genedx.com/test-catalog/disorders/achondroplasia-ach/ or reading through the FGFR3 in a sequencing test.

Of course, if there is a unknown change in the FGFR3 gene resulting in achondroplasia in the family, they can just test for that gene change.

After birth

A diagnosis of achondroplasia is usually made not through genetic testing but by physical examination and review of X-rays. There is a very specific set of criteria looking at health issues, symptoms, and measurements that doctors use to determine if a person has achondroplasia.

Genetic testing can confirm a diagnosis of achondroplasia, but is not required for the diagnosis. This is done by obtaining a sample of DNA from a person, typically through a blood draw. The sample is first tested for the two most common changes in the FGFR3 gene that are associated with achondroplasia. One of these two changes is present in about 99% of people with a clinical diagnosis of achondroplasia. Genetic laboratories can also look at the entire FGFR3 gene (gene sequencing) to detect much more rare genetic changes. This approach may be beneficial when it is unclear whether a diagnosis of hypochondroplasia or achondroplasia is more appropriate. There are several labs that do this type of testing and there is a list on the Genetests site.

There is also the option of a genetic testing panel that tests for achondroplasia AND other causes of dwarfism. A good example of that is the Disproportionate Short Stature: Sequencing Panel at EGL Genetics. Of course, if there is a unknown change in the FGFR3 gene resulting in achondroplasia in the family, they can just test for that gene change.

Regular Checkups

If someone has achondroplasia there are important things to check on a regular basis. Generally for newly diagnosed child, it is recommended that they have:

  • Genetics clinic appointment
  • Skeletal Dysplasia clinic appointment, if possible
  • Comparison of a child's height, weight, and head size to other children of their age with achondroplasia
  • CT scan of brain to acquire baseline
  • Supervision of the craniocervical junction (skull to spine connection): healthcare provider should take a neurologic history, provide a clinical examination, and order a CT scan of the craniocervical junction. A sleep study should also be offered.
References
  • Ask a ThinkGenetic Counselor, November 2, 2016
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More Diagnosis and Testing Content

How do I get tested for achondroplasia?

Is there newborn testing for achondroplasia?

Is there more than one test for achondroplasia?

Who else in my family should I test for achondroplasia?

How do I get tested for achondroplasia?

A diagnosis of achondroplasia is typically made not through genetic testing but by physical examination and review of X-rays. There is a very specific set of criteria doctors use to determine if a person has achondroplasia. To learn more about the diagnostic criteria for achondroplasia, review the Gene Facts information sheet on the diagnosis of achondroplasia.

Genetic testing can confirm a diagnosis of achondroplasia, but is not required for the diagnosis. This is done by obtaining a sample of DNA from a person, typically through a blood draw. The sample is first tested for the two most common changes in the FGFR3 gene that are associated with achondroplasia. One of these two changes is present in about 99% of people with a clinical diagnosis of achondroplasia. Genetic laboratories can also look at the entire FGFR3 gene (gene sequencing) to detect much more rare genetic changes. This approach may be beneficial when it is unclear whether a diagnosis of hypochondroplasia or achondroplasia is more appropriate. Generally though, it is recommended to begin with targeted genetic testing. To discuss arranging genetic testing for achondroplasia, contact a local genetic counselor. You can find one through the National Society of Genetic Counselors Find A Genetic Counselor search page.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
  • http://genefacts.org/index.php?option=com_content&view=article&id=470&Itemid=639
Is there newborn testing for achondroplasia?

As of June 2016, achondroplasia is not on the Recommended Uniform Screen Panel (RUSP). The RUSP is created by the Health Resources and Services Administration, and states use this list to guide what conditions they screen for on newborn screening. It should be noted that almost all babies with achondroplasia will be suspected as having achondroplasia or another form of dwarfism after initial examination by a pediatrician.

References
  • http://www.hrsa.gov/advisorycommittees/mchbadvisory/heritabledisorders/recommendedpanel/
Is there more than one test for achondroplasia?

There are two types of genetic testing available for achondroplasia. Targeted genetic testing looks for the two most common changes in the FGFR3 gene that are associated with achondroplasia. This testing finds the mutation in around 99% of people with achondroplasia. Genetic laboratories can also look at the entire FGFR3 gene (gene sequencing) to detect genetic changes. This approach may be beneficial when it is unclear whether a diagnosis of hypochondroplasia or achondroplasia is more appropriate. Generally though, it is recommended to begin with targeted genetic testing.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/
Who else in my family should I test for achondroplasia?

Unless a person has significant symptoms of achondroplasia, there is no need to test other relatives. It is not possible to be a carrier of achondroplasia like it is for some other conditions, such as cystic fibrosis or sickle cell disease.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1152/

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