Baby is a carrier of G542x, Negative Sweat Test

Question

I had a question. Our daughter is a carrier of G542x. Her sweat test was negative. My wife and I are starting to think about having another baby and am confused about what I have found online.

If I am the carrier of G542x and my wife has any of the other 1800 known mutation, can my next child still inherit CF? Or does it have to be the exact same gene? (g542x)

Sincerely,

Max

Answer

Dear Max,

Thank you for your question. Cystic fibrosis requires disease-causing mutations in both of the genes that code for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. There many potential combinations and therefore many possible levels of disease and severity. If you are a carrier of a mutation and your wife also carries a mutation then the possibility of having a child with CF is 1 in 4. However, as I have stated above, there are many different mutations that affect disease in different ways, and at this time it is not clear from your question if it is known that your wife even carries another mutation.
In summary, you do not have to have 2 identical mutations of the CFTR-gene. It is difficult to comment on future children as the genetics of the parents are not known in this case. Obviously if you both carry mutations then the risk of a child with CF is higher (however once again the combination of genetics can have a variable clinical presentation, severity and prognosis).
I hope this helps and if you have any further questions, please feel free to ask.


Dr Stephen Rowan
Queen's University Belfast and Belfast City Hospital
Belfast

12.12.2012

The answer is edited by: Prof Judy Bradley