another genetic testing

Question

(to dr A. Sobczyńska)
The child was examined and has F508 del mutation (examination was done 11 years ago). Should I examined the child again toward another mutation? The second child is not sick (sweat test). Should I perform genetic tests in the second child toward a CF carrier state?

Answer

Dear Questioner,
it is a bit tricky in your case to give a straight answer as some points are not coming up really clear which are necessary for giving a straight answer. I assume that your first child is suffering from CF as you mention that your second child is not sick.
Then you mention that F508 del mutation has been found in your first child; but what we do not get from the information is if they found F508 del mutation on both genes in that child that suffers from CF? In that case one does not need to examine the ill child again towards another mutation because we know the two mutations on both genes. Then, the second child of course could be tested, if it carries also one gene with F508 del mutation (carrier).
In case, however, that the ill child had been tested and F508 del mutation has been found only on one gene, and the child is obviously suffering from CF, then one could assume, that probably with the test 11 years ago, the other mutation on the other gene has not been found and then it would make sense to do another genetic testing on the ill child in order to find the second CF mutation (use a test with a wider mutations panel). After that, the second child could be tested for either having F508 del or for having the other CF mutation which is not known until now.

Contact with dr A. Sobczyńska: Dept. of Medical Genetics, Mother and Child Institute, 17a Kasprzaka str., 01-211 Warszawa (phone 022 327 73 61).
Best regards, Natalia Kobelska-Dubiel, MD, PhD

02.02.2009