Antley-Bixler syndrome

Diagnosis and Testing

How do I get tested for Antley-Bixler syndrome?

The presence of craniosynostosis (premature closure of skull bones) and radiohumeral synostosis (fusion of adjacent arm bones) at birth are the minimum criteria for a diagnosis of ABS. However, it is also important to distinguish between the two types of ABS due to the difference in inheritance patterns and the vulnerability to different risk factors. The two types can be distinguished through clinical findings of ambiguous genitalia, or a biochemical blood test checking for steroid abnormalities. Molecular genetic testing is desirable to confirm a diagnosis of ABS and which type is, especially when physical and laboratory findings are inconclusive.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist and other medical specialist.

To discuss arranging genetic testing for Antley-Bixler syndrome, contact a local genetic counselor. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
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More Diagnosis and Testing Content

Is there newborn testing for Antley-Bixler syndrome?

Is there more than one test for Antley-Bixler syndrome type with genital anomalies and disordered steroidogenesis?

Who else in my family should have testing for Antley-Bixler syndrome type with genital anomalies and disordered steroidogenesis?

How do they make a diagnosis of Antley-Bixler syndrome?

What type of sample should be taken for Antley-Bixler syndrome genetic testing?

Is there more than one test for Antley-Bixler syndrome type without genital anomalies and disordered steroidogenesis?

Who else in my family should have testing for Antley-Bixler syndrome type without genital anomalies and disordered steroidogenesis?

Is there newborn testing for Antley-Bixler syndrome?

Newborn screening does not currently test for Antley-Bixler syndrome (ABS). However, some cases are detected through a positive newborn screening for congenital adrenal hyperplasia. All newborns in the United States are screened for 21-hydroxylase deficiency, known as classic congenital hyperplasia. ABS with genital anomalies and disordered steroidogenesis is caused by a mutation in the POR gene. Disruptions to the POR gene reduces the activity of an enzyme required for steroid hormone production, cytochrome P450 oxidoreductase. Consequently, this disorder presents with a deficiency of 21-hydroxylase. Newborn screening does not appear to be sensitive enough to detect all individuals with ABS with genital anomalies and disordered steroidogenesis.

If you are concerned that your newborn may have this disorder, talk to your child's pediatrician to about testing or further workup.

References
Is there more than one test for Antley-Bixler syndrome type with genital anomalies and disordered steroidogenesis?

Antley-Bixler syndrome (ABS) with genital anomalies and disordered steroidogenesis can be detected through biochemical and molecular genetic testing.

Biochemical Testing

ABS with genital anomalies and disordered steroidogenesis disrupts enzymatic function within the cholesterol and steroid synthesis pathways. Therefore, individuals with this type of ABS will have characteristic abnormalities of both sterol and steroid metabolism. These biochemical levels can be tested through blood and urine samples.

Molecular Genetic Testing

Molecular testing can confirm the diagnosis and differentiate between the two types of ABS. There are three genetic testing approaches:

  • Single-gene testing: POR gene is sequenced followed by deletion/duplication analysis if no pathogenic variant found
  • Multigene panel: A genetic test that looks at POR and other genes of interest. Methods of testing may include sequencing, deletion/duplication analysis, and/or other non-sequencing-based tests
  • Comprehensive genomic testing: This testing can include exome sequencing, mitochondrial sequencing, and genome sequencing. Useful when diagnosis is unclear.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist, genetic counselor, and other medical specialist.

A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
Who else in my family should have testing for Antley-Bixler syndrome type with genital anomalies and disordered steroidogenesis?

Antley-Bixler syndrome (ABS) with genital anomalies and disordered steroidogenesis is an autosomal recessive condition. Genes exist in pairs and autosomal recessive conditions occur when there are changes to both gene copies. Individuals with one altered gene, referred to as carriers, do not develop the condition and typically do not have any symptoms. Parents of an individual with this type of ABS are obligated carriers for the condition. Siblings of the affect individual have a 50% chance of being a carrier of this conditions and, therefore, may consider testing.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist, genetic counselor, and other medical specialist.

A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
How do they make a diagnosis of Antley-Bixler syndrome?

The presence of craniosynostosis (premature closure of skull bones) and radiohumeral synostosis (fusion of adjacent arm bones) at birth are the minimum criteria for a diagnosis of Antley-Bixler syndrome. Molecular genetic testing is desirable to confirm the diagnosis and to differentiate between the two types of ABS: ABS with genital anomalies and disordered steroidogenesis, and ABS without genital anomalies and disordered steroidogenesis.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist and other medical specialist.

To discuss arranging genetic testing for Antley-Bixler syndrome, contact a local genetic counselor. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
What type of sample should be taken for Antley-Bixler syndrome genetic testing?

A blood (1.5 - 3.0 mL) or a saliva (1-2 mL) sample can be used for Antley-Bixler syndrome genetic testing.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist and other medical specialist.

To discuss arranging genetic testing for Antley-Bixler Syndrome, contact a local genetic counselor. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
Is there more than one test for Antley-Bixler syndrome type without genital anomalies and disordered steroidogenesis?

Antley-Bixler syndrome (ABS) without genital anomalies and disordered steroidogenesis is confirmed though molecule genetic testing. ABS without genital anomalies and disordered steroidogenesis is caused by a mutation in the FGFR2 gene, but similar presentations are found with mutations in FGFR1 and FGFR3. Therefore, molecular genetic testing of FGFR1, FGFR2, and FGFR3 may be helpful when diagnosis is unclear or questionable.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist, genetic counselor, and other medical specialist.

A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
Who else in my family should have testing for Antley-Bixler syndrome type without genital anomalies and disordered steroidogenesis?

Antley-Bixler syndrome (ABS) without genital anomalies and disordered steroidogenesis is an autosomal dominant condition. Genes exist in pairs and autosomal dominant conditions occur when a change to one copy of a gene is enough to cause the condition. This type of ABS may be the result of a new change in that individual or it may be inherited from an affected parent. Therefore, it is recommended to evaluate parents through clinical, radiographic, and molecular genetic evaluation. Once the status of the parents is known other family members' risk can be determined. If a parent is affect, his or her family members are at risk and may consider testing. Furthermore, if the change in the gene came from an affected parent, each child of the parent will have a 50% chance of having this condition. Prenatal testing is available is mutation is known.

Discuss with your doctor about any concerns you have or for a referral to a medical geneticist, genetic counselor, and other medical specialist.

A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website.

References

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