Is Congenital Central Hypoventilation Syndrome hereditary?

Congenital Central Hypoventilation Syndrome (CCHS) is a genetic condition caused by mutations in the PHOX2B gene, but it is not always inherited from a parent. While most cases arise from a spontaneous (de novo) mutation, approximately 10% to 25% of individuals with Congenital Central Hypoventilation Syndrome inherit the mutation from an affected parent who may have a milder, undiagnosed form of the condition.

Is Congenital Central Hypoventilation Syndrome hereditary?

Congenital Central Hypoventilation Syndrome is classified as a genetic condition, meaning it is caused by changes in the DNA. It follows an autosomal dominant inheritance pattern. This means that a person only needs one copy of the mutated PHOX2B gene to be affected by Congenital Central Hypoventilation Syndrome. While the term "hereditary" implies the condition is passed down through families, it is important to distinguish this from "genetic." A condition is genetic if it results from a mutation, but it is only hereditary if that mutation is passed from parent to child. In many cases of Congenital Central Hypoventilation Syndrome, the mutation occurs as a de novo event, meaning it appears for the first time in the affected individual without a family history.

What is the risk of passing on Congenital Central Hypoventilation Syndrome?

For an individual who has been diagnosed with Congenital Central Hypoventilation Syndrome, the risk of passing the PHOX2B mutation to each child is 50%. Because the condition can present with variable expressivity—meaning some family members may have very mild symptoms that went undetected—it is essential for parents of an affected child to undergo genetic testing. Even if a parent has no symptoms, they could potentially carry the mutation in a small percentage of their cells (germline mosaicism) or have a very mild phenotype. Clinical geneticists emphasize that families should not assume a lack of symptoms in parents equates to a lack of genetic risk.

How is genetic testing used for Congenital Central Hypoventilation Syndrome?

Genetic testing for Congenital Central Hypoventilation Syndrome is the gold standard for confirmation. It focuses on analyzing the PHOX2B gene, specifically looking for polyalanine repeat expansion mutations (PARMs) or non-polyalanine repeat expansion mutations (NPARMs). Testing is recommended in the following scenarios:

• Diagnostic confirmation: When a newborn or infant presents with unexplained hypoventilation, particularly during sleep.


• Parental testing: To determine if either parent carries the mutation, which informs recurrence risk for future pregnancies.


• Prenatal and preimplantation diagnosis: Families with a known PHOX2B mutation may pursue prenatal testing (via chorionic villus sampling or amniocentesis) or preimplantation genetic testing (PGT) through IVF to select embryos without the mutation.

The role of genetic counseling in this community

At DiseaseMaps.org, where 94 people with Congenital Central Hypoventilation Syndrome have shared their experiences, genetic counseling is a vital bridge between diagnosis and family planning. A genetic counselor helps families navigate the complexities of autosomal dominant inheritance and provides support regarding the emotional weight of a genetic diagnosis. They assist in interpreting test results, calculating specific recurrence risks, and discussing reproductive options for those who carry the PHOX2B mutation.

Next steps

• Consult a clinical geneticist to discuss PHOX2B testing if you or a family member suspects a diagnosis of Congenital Central Hypoventilation Syndrome.


• Request a referral for genetic counseling to discuss family planning and the implications of the 50% recurrence risk.


• Connect with the DiseaseMaps.org community to share experiences and find peer support from others navigating the genetic aspects of Congenital Central Hypoventilation Syndrome.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment; always seek the guidance of your physician or other qualified health provider with any questions regarding a medical condition.

References

• National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD): Congenital Central Hypoventilation Syndrome.


• Online Mendelian Inheritance in Man (OMIM): #209880 - Central Hypoventilation Syndrome, Congenital.


• Orphanet: Congenital Central Hypoventilation Syndrome (ORPHA:415).


• PHOX2B-related disorders: GeneReviews (NCBI Bookshelf).