Thanatophoric dysplasia

Diagnosis and Testing

How is thanatophoric dysplasia diagnosed?

It can be difficult to make the diagnosis of thanatophoric dysplasia during pregnancy, because there are many types of skeletal dysplasias (disorders of the skeleton) that look similar to one another during pregnancy. A clinical diagnosis can usually be made after the baby is born through a physical examination and review of a full set of skeletal x-rays. Because of the large number of skeletal dysplasia and the various associated genetic tests, it is ideal to speak to a pediatric geneticist with expertise in skeletal dysplasias for specific testing recommendations. A listing of medical geneticists can be found at the American College of Medical Geneticists website (

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Are newborns usually tested for thanatophoric dysplasia?

What type of tests are done to diagnose thanatophoric dysplasia?

Who should be tested for thanatophoric dysplasia in my family?

Are newborns usually tested for thanatophoric dysplasia?

Newborns are not routinely tested for thanatophoric dysplasia, however, most women who have had prenatal care during their pregnancy are aware if their baby is thought to have a skeletal dysplasia based on abnormal ultrasound findings. If your doctor is concerned about the possibility of thanatophoric dysplasia during your pregnancy, or after the birth of your baby, genetic testing of the FGFR3 gene can be undertaken.

What type of tests are done to diagnose thanatophoric dysplasia?

Thanatophoric dysplasia is a type of skeletal disorder that is caused by a genetic change in the gene FGFR3. A diagnosis of thanatophoric dysplasia might be based on clinical features (i.e. a physical examination and x-rays of the baby's bones), or on the results of a genetic test of the FGFR3 gene. If a genetic change in the FGFR3 gene is identified and has been reported previously in one or more affected individuals, this is usually enough evidence for the genetic testing laboratory to state that the change/mutation confirms the clinical diagnosis.

Who should be tested for thanatophoric dysplasia in my family?

Because thanatophoric dysplasia is almost always due to a de novo mutation, the chance of it recurring in a family is considered very low. There is a theoretical risk that a parent could have something called i]gonadal mosaicism, where some or all of that person's gonad cells (eggs or sperm) have a mutation in the FGFR3 gene, even though none of the other cells in that person's body have the mutation. In this situation, the parent him or herself would be healthy, but there would be a risk of having more than one child with thanatophoric dysplasia. So far, gonadal mosaicism has never been reported in thanatophoric dysplasia.

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